Duddell Street Acquisition : Proxy Statement for EGM

PROXY STATEMENT FOR

EXTRAORDINARY GENERAL MEETING OF DUDDELL STREET ACQUISITION CORP.

(A CAYMAN ISLANDS EXEMPTED COMPANY)

PROSPECTUS FOR

149,063,848 SHARES OF CLASS A COMMON STOCK, 8,179,624 SHARES OF CLASS B COMMON

STOCK, 13,750,000 REDEEMABLE WARRANTS AND

13,750,000 SHARES OF CLASS A COMMON STOCK UNDERLYING REDEEMABLE WARRANTS

OF

DUDDELL STREET ACQUISITION CORP.

(AFTER ITS DOMESTICATION AS A CORPORATION INCORPORATED IN THE STATE OF DELAWARE), THE CONTINUING ENTITY FOLLOWING THE DOMESTICATION, WHICH WILL BE RENAMED "FISCALNOTE HOLDINGS, INC." IN CONNECTION WITH THE BUSINESS COMBINATION DESCRIBED HEREIN

On November 7, 2021, the board of directors of Duddell Street Acquisition Corp. (the "DSAC

Board"), a Cayman Islands exempted company limited by shares (which shall domesticate as a Delaware corporation in connection with the consummation of the transactions contemplated hereby) ("DSAC," "we," "us" or "our"), approved an Agreement and Plan of Merger, dated November 7, 2021, by and among DSAC, Grassroots Merger Sub, Inc., a wholly owned subsidiary of DSAC ("Merger Sub"), and FiscalNote Holdings, Inc. ("FiscalNote") (as it may be amended and/or restated from time to time, including by the First Amendment to Agreement and Plan of Merger, dated May 9, 2022 (the "First Amendment"), the "Business Combination Agreement"), copies of which are attached to this proxy statement/prospectus as Annex A-1and Annex A-2, respectively. If the Business Combination Agreement is approved and adopted by DSAC's shareholders and other closing conditions contemplated by the Business Combination Agreement are satisfied, DSAC intends to effect a deregistration under the Cayman Islands Companies Act (As Revised) and a domestication under Section 388 of the Delaware General Corporation Law, as amended (the "DGCL"), pursuant to which DSAC's jurisdiction of incorporation will be changed from the Cayman Islands to the State of Delaware (the "Domestication"), and, on the terms and subject to the conditions set forth in the Business Combination Agreement and in accordance with the DGCL, Merger Sub will merge with and into FiscalNote, with FiscalNote surviving the merger as a wholly owned subsidiary of DSAC (the "Business Combination"). In addition, in connection with the consummation of the Business Combination, DSAC will be renamed "FiscalNote Holdings, Inc." As used herein, "New DSAC" refers to DSAC after the Domestication but prior to consummation of the Business Combination and "New FiscalNote" refers to DSAC after consummation of the Business Combination.

In connection with the Domestication, (i) each issued and outstanding Class A ordinary share, par value $0.0001 per share (the "DSAC Class A ordinary share"), and each issued and outstanding Class B ordinary share, par value $0.0001 per share (the "DSAC Class B ordinary share"), of DSAC will be converted into one share of Class A common stock, par value $0.0001 per share, of New DSAC (the "New DSAC Class A Common Stock"); (ii) each issued and outstanding whole warrant to purchase Class A ordinary shares of DSAC will automatically represent the right to purchase one share of New DSAC Class A Common Stock at an exercise price of $11.50 per share on the terms and conditions set forth in the warrant agreement, dated October 28, 2020, between DSAC and Continental Stock Transfer & Trust Company ("Continental"), as warrant agent (the "Warrant Agreement"); and (iii) the governing documents of DSAC will be amended and restated and become the certificate of incorporation and the bylaws of New DSAC, copies of which are attached to this proxy statement/prospectus as Annex Band Annex C, respectively. In connection with clauses (i) and (ii) of this paragraph, each issued and outstanding unit of DSAC that has not been previously separated into the underlying Class A ordinary shares of DSAC and the underlying warrants of DSAC prior to the Domestication will be canceled and will entitle the holder thereof to one share of New DSAC Class A Common Stock and one-half of one warrant representing the right to purchase one share of New DSAC Class A Common Stock at an exercise price of $11.50 per share on the terms and subject to the conditions set forth in the Warrant Agreement.

At the closing of the Business Combination (the "Closing"), at least one day following the consummation of the Domestication, Merger Sub will merge with and into FiscalNote (the "Merger"), with FiscalNote as the surviving company in the Merger and, after giving effect to the Merger, FiscalNote will be a wholly owned direct subsidiary of New FiscalNote (the time at which the Merger becomes effective being

referred to as the "Effective Time"). The principal executive offices of the post-Business Combination company will be located in Washington, D.C. We are not, and will not, undertake an initial business combination with any entity with principal business operations in mainland China, Hong Kong, or Macau. DSAC's IPO proceeds are in a trust account located in the United States.

Under the Business Combination Agreement, DSAC has agreed to acquire all of the issued and outstanding shares of FiscalNote, other than dissenting shares, in exchange for Per Share Merger Consideration (as defined below) in the form of common stock of New FiscalNote ("New FiscalNote common stock"), plus Per Share Earnout Consideration (as defined below) subject to each Triggering Event (as defined below). FiscalNote stockholders will receive consideration in the form of shares of Class A common stock of New FiscalNote ("New FiscalNote Class A common stock") and/or Class B common stock of New FiscalNote ("New FiscalNote Class B common stock"), as determined in accordance with the Business Combination Agreement. Following the Domestication and immediately prior to the consummation of the Business Combination, the holders of DSAC Class A ordinary shares that do not elect to redeem their shares will receive a distribution of 0.57 shares of New FiscalNote Class A common stock for each share of New DSAC Class A Common Stock received in the Domestication (the "Bonus Shares"). In addition, unlike other business combinations in which issuances of bonus shares are contemplated, certain affiliates of the Sponsor will also receive an issuance of 0.57 Bonus Shares of New FiscalNote Class A common stock for each share of New DSAC Class A Common Stock they subscribe for pursuant to the Backstop Agreement described herein. Given that the Sponsor has agreed not to redeem DSAC ordinary shares held by it pursuant to that certain letter agreement executed in connection with DSAC's IPO, the receipt of the Bonus Shares by affiliates of the Sponsor, including the Backstop Parties, will not incentivize the Sponsor or its affiliates, including the Backstop Parties, not to redeem.

DSAC and FiscalNote currently do not have any operations in mainland China. Accordingly, notwithstanding that the Sponsor is located in Hong Kong and a majority of DSAC's executive officers are located in or have significant ties to Hong Kong prior to the completion of the Business Combination, the laws and regulations of the People's Republic of China (''PRC'') do not currently have any impact on DSAC's business, financial condition and results of operations because, pursuant to the Basic Law of the Hong Kong Special Administrative Region (the "Basic Law"), which is a national law of the PRC and the constitutional document for Hong Kong, national laws of the PRC are not applied in Hong Kong, except for those listed in Annex III of the Basic Law, which are confined to laws relating to defense and foreign affairs as well as other matters outside the autonomy of Hong Kong.

If certain PRC laws and regulations were to become applicable to a company such as us in the future, the application of such laws and regulations may have a material adverse impact on us, including our ability to continue our Business Combination or seek another target company, any of which may cause the value of our securities to significantly decline or become worthless. For example, if the PRC Data Security Law were to apply to us, we could become subject to data security and privacy obligations, including the need to conduct a national security review of data activities that may affect the national security of the PRC. Similarly, if the Measures for Cybersecurity Review issued by 13 Chinese governmental authorities lead by the Cyberspace Administration of China (the "Cybersecurity Review Measures") on December 28, 2021, which relates to data security and overseas listing of mainland Chinese businesses, were to apply to us because we have Hong Kong exposure, we may be required to apply for a cybersecurity review by the Cybersecurity Review Office of the PRC prior to completing our Business Combination. As DSAC, FiscalNote and their affiliated entities do not have any operations in mainland China and have not been engaged in any data activities that affect or may affect the national security of the PRC, we believe, based on our inquiries with Fangda Partners, our PRC legal advisor, none of DSAC, FiscalNote, or any of their affiliated entities is required to obtain any approval or permission from the China Securities Regulatory Commission (CSRC), the Cyberspace Administration of China (CAC) or any other PRC governmental authority as of the date of this proxy statement/prospectus to consummate the Business Combination or issue the securities being registered to investors outside of the PRC pursuant to this proxy statement/prospectus. However, there remains significant uncertainty as to the enactment, interpretation and implementation of regulatory requirements related to overseas securities offerings and other capital markets activities. If it is determined in the future that the approvals or permissions of the CSRC, the CAC or any other government authorities are required for consummation of the Business Combination, and we or New FiscalNote do not receive or maintain such approval, inadvertently conclude that such permissions or approvals are not required, or applicable laws, regulations, or interpretations change and we are required to obtain such permissions or approvals in the future, we or New FiscalNote may face sanctions by the CSRC, the CAC or other PRC government authorities. These government authorities may impose fines and penalties on us, limit our operations in China, or take other actions that could have a material adverse effect on our business, financial

condition, results of operations and prospects, as well as the trading price of our securities. The CSRC, the CAC or other PRC regulatory agencies also may take actions requiring us, or making it advisable for us, to suspend or terminate the Business Combination before the Closing. Consequently, if you engage in market trading or other activities in anticipation of and prior to the Closing, you do so at the risk that the Business Combination may not occur.

In addition, while we believe that the recent statements or regulatory actions by the relevant agencies of the PRC government, including those in relation to the PRC Data Security Law, the Cybersecurity Review Measures, the PRC Personal Information Protection Law and variable interest entities, and the anti-monopoly enforcement actions taken by relevant PRC government authorities, should not have any material adverse impact on us, FiscalNote's post-Business Combination operations, the value of our securities, or our ability to offer or continue to offer securities to investors, there is no guarantee that will continue to be the case or that the PRC government will not seek to intervene or influence our operations at any time. Should such statements or regulatory actions apply to a company such as us in the future, it would likely have a material adverse impact on our business, financial condition and results of operations, our ability to accept foreign investments and our ability to offer or continue to offer securities to investors on a U.S. or other international securities exchange, any of which may cause the value of our securities, including our units, shares and warrants, to significantly decline or become worthless. We cannot predict the extent of such impact if such events were to occur. See "Risk Factors - Risks Related to DSAC - Risks Related to DSAC's Location in Hong Kong."

"Per Share Merger Consideration" means: (i) with respect to shares of Class A common stock of FiscalNote ("FiscalNote Class A common stock") and shares of preferred stock of FiscalNote ("FiscalNote preferred stock") immediately prior to the Effective Time, a number of shares of New FiscalNote Class A common stock equal to the Exchange Ratio (as hereinafter defined) and (ii) with respect to shares of Class B common stock of FiscalNote ("FiscalNote Class B common stock" and, together with the FiscalNote Class A common stock, "FiscalNote common stock") immediately prior to the Effective Time, a number of shares of New FiscalNote Class B common stock equal to the Exchange Ratio. "Exchange Ratio" means the quotient obtained by dividing (i) the Per Share Equity Value by (ii) $10.00 per share. "Per Share Equity Value" means the quotient obtained by dividing (i) the Company Value (as defined in the Business Combination Agreement), by (ii) the Company Shares Outstanding (as defined in the Business Combination Agreement).

At the Effective Time, all of the warrants to purchase FiscalNote Class A common stock or FiscalNote preferred stock that are outstanding and unexercised immediately prior to the Effective Time ("FiscalNote Warrants") will be deemed automatically exercised and converted into the right to receive (such right, a "New FiscalNote Warrant") (I) that number of shares of New FiscalNote Class A common stock determined by finding the quotient of (i) (A) the number of shares of FiscalNote Class A common stock underlying the vested portion of the FiscalNote Warrant, multiplied by (B) (x) the Per Share Equity Value less (y) the per share exercise price of such FiscalNote Warrant, minus (C) the applicable withholding taxes relating to the deemed exercise of such FiscalNote Warrant (to the extent the number calculated under this sub-clause (i) is a positive number), divided by (ii) $10.00 per share and (II) upon a Triggering Event, the applicable Per Share Earnout Consideration in accordance with the Business Combination Agreement, in each case without interest.

At the Effective Time, all of the subordinated convertible promissory notes issued by FiscalNote that have not converted by their own terms in connection with the transaction and are outstanding and unexercised immediately prior to the Effective Time ("FiscalNote Convertible Notes") will be automatically assumed and converted into a convertible note issued by New FiscalNote, with a right of conversion into shares of New FiscalNote Class A common stock.

At the Effective Time, all of the options exercisable for FiscalNote Class A common stock (each, a "FiscalNote Option") that are outstanding and unexercised immediately prior to the Effective Time will be automatically assumed and converted into a stock option (each, a "Converted Option") to purchase shares of New FiscalNote Class A common stock. Each such Converted Option as so assumed and converted shall continue to have and be subject to substantially the same terms and conditions as were applicable to such FiscalNote Option immediately before the Effective Time (including vesting (if applicable), expiration date and exercise provisions), except that, as of the Effective Time, each such Converted Option as so assumed and converted shall be exercisable for (I) that number of shares of New FiscalNote Class A common stock determined by multiplying the number of FiscalNote Class A common stock subject to such FiscalNote Option immediately prior to the Effective Time by the Exchange Ratio, which product shall be rounded

down to the nearest whole number of shares, at a per share exercise price determined by dividing the per share exercise price of such FiscalNote Option immediately prior to the Effective Time by the Exchange Ratio, which quotient shall be rounded up to the nearest whole cent and (II) upon a Triggering Event, the applicable Per Share Earnout Consideration in accordance with the Business Combination Agreement; provided that the exercise price and the number of shares of FiscalNote Class A common stock purchasable under each Converted Option shall be determined in a manner consistent with the requirements of applicable laws and regulations.

At the Effective Time, all of the vested restricted stock units to acquire shares of FiscalNote Class A common stock ("Vested FiscalNote RSUs") outstanding immediately prior to the Effective Time will be automatically deemed settled and converted into the right to receive (I) that number of shares of New FiscalNote Class A common stock determined by finding the quotient of (i) (A) the number of shares of FiscalNote Class A common stock underlying such Vested FiscalNote RSU, multiplied by (B) the Per Share Equity Value, minus (C) the applicable withholding taxes relating to the deemed settlement of such Vested FiscalNote RSU (to the extent the number calculated under this sub-clause (i) is a positive number), divided by (ii) $10.00 per share and (II) upon a Triggering Event, the applicable Per Share Earnout Consideration in accordance with the Business Combination Agreement.

At the Effective Time, all of the unvested restricted stock units to acquire shares of FiscalNote Class A common stock ("Unvested FiscalNote RSUs") outstanding immediately prior to the Effective Time will be automatically assumed and converted into a restricted stock unit (each, a "Converted RSU") of shares of New FiscalNote Class A common stock. Each such Converted RSU as so assumed and converted shall continue to have and be subject to substantially the same terms and conditions as were applicable to such Unvested FiscalNote RSU immediately before the Effective Time (including vesting (if applicable) and payment provisions), except that, as of the Effective Time, each such Converted RSU as so assumed and converted shall be settled for (i) that number of shares of New FiscalNote Class A common stock determined by multiplying the number of FiscalNote common stock subject to such Unvested FiscalNote RSU immediately prior to the Effective Time by the Exchange Ratio, which product shall be rounded down to the nearest whole number of shares and (ii) upon a Triggering Event, the applicable Per Share Earnout Consideration in accordance with the Business Combination Agreement.

As described above, the Business Combination Agreement contemplates that (i) (a) the holders of FiscalNote common stock, FiscalNote Warrants and Vested FiscalNote RSUs outstanding immediately prior to the Effective Time and (b) holders of FiscalNote Options that are vested ("Vested FiscalNote Options") and unexercised immediately before the Effective Time, holders of FiscalNote Options that are unvested ("Unvested FiscalNote Options") and that hold related Converted Options that are vested as of such Triggering Event and holders of Unvested FiscalNote RSUs that hold related Converted RSUs that are vested as of such Triggering Event, will collectively be entitled to receive the Per Share Earnout Consideration, and (ii) holders of Unvested FiscalNote Options that are unexercised, issued and outstanding and holders of Unvested FiscalNote RSUs outstanding, in each case as of immediately prior to the Effective Time, shall be issued restricted stock units in respect of one share of New FiscalNote Class A common stock ("Earnout RSUs") upon the occurrence of a Trigging Event to the extent the Converted Option related to such Unvested FiscalNote Option or the Converted RSU related to such Unvested FiscalNote RSU is outstanding and unvested as of the occurrence of a Triggering Event, in each case during the five years after the closing date of the Business Combination (the "Earnout Period") and based on the conditions below (collectively, the "Triggering Events"):

• the dollar volume-weighted average price of one share of New FiscalNote Class A common stock on the NYSE or Nasdaq (as defined below) is greater than or equal to $10.50 for any 10 trading days within any period of 20 consecutive trading days during the Earnout Period;
• the dollar volume-weighted average price of one share of New FiscalNote Class A common stock on the NYSE or Nasdaq is greater than or equal to $12.50 for any 10 trading days within any period of 20 consecutive trading days during the Earnout Period;
• the dollar volume-weighted average price of one share of New FiscalNote Class A common stock on the NYSE or Nasdaq is greater than or equal to $15.00 for any 10 trading days within any period of 20 consecutive trading days during the Earnout Period;
• the dollar volume-weighted average price of one share of New FiscalNote Class A common stock on the NYSE or Nasdaq is greater than or equal to $20.00 for any 10 trading days within any period of 20 consecutive trading days during the Earnout Period; and

• the dollar volume-weighted average price of one share of New FiscalNote Class A common stock on the NYSE or Nasdaq is greater than or equal to $25.00 for any 10 trading days within any period of 20 consecutive trading days during the Earnout Period.

For illustrative purposes, up to 95,931,668 shares of New FiscalNote capital stock are estimated to be issued in connection with the Business Combination, consisting of (a) 87,752,044 shares of New FiscalNote Class A common stock and (b) 8,179,624 shares of New FiscalNote Class B common stock. Up to 10,265,804 shares of New FiscalNote Class A common stock are estimated to be reserved for issuance upon exercise or settlement of options and RSUs of New FiscalNote issued and outstanding immediately following the consummation of the Business Combination. Additionally, up to 19,171,000 shares of New FiscalNote Class A common stock (including shares reserved for issuances upon settlement of Earnout RSUs) are estimated to be issued as earnout consideration pursuant to the Business Combination upon occurrence of the Triggering Events.

The foregoing numbers of New FiscalNote securities to be issued in connection with the Business

Combination were based on an Exchange Ratio calculated as the quotient of (A) the sum of $1 billion (the Company Value as defined in the Business Combination Agreement) plus the aggregate exercise price payable with respect to vested FiscalNote options and FiscalNote warrants (assumed to be approximately

11.0 million), divided by (B) the total number of issued and outstanding FiscalNote shares (assumed to be 85,918,941), taking into account the total number of shares issued or issuable as a result of any exercise or conversion of all FiscalNote equity securities outstanding immediately prior to Closing, divided by $10.00. As of April 27, 2022, the Exchange Ratio is expected to be approximately 1.17.

If the Converted Option or Converted RSU related to such Unvested FiscalNote Option or Unvested FiscalNote RSU, as applicable, is forfeited after the Effective Time but prior to such Triggering Event, no Earnout RSUs will be issued for such Unvested FiscalNote Option or Unvested FiscalNote RSU, as applicable. The right to receive Earnout RSUs that have been forfeited shall be reallocated pro rata to the other holders of Converted Options and Converted RSUs then outstanding with holders of vested Converted Options and Converted RSUs receiving Earnout RSU Shares and holders of unvested Converted Options and Converted RSUs receiving Earnout RSUs that vest pro rata in accordance with the remaining vesting schedule of the underlying unvested Converted Option or Converted RSU.

"Per Share Earnout Consideration" means, with respect to each Triggering Event, a number of shares of New FiscalNote common stock equal to (i) the number of shares of New FiscalNote Class A common stock equal to 3% of the number of shares of New FiscalNote common stock outstanding immediately after Closing, divided by (ii) the sum of (A) the Company Shares Outstanding, plus (B) the number of shares of FiscalNote common stock issued or exercisable upon the exercise of all Unvested FiscalNote Options and settlement of Unvested FiscalNote RSUs as of immediately prior to the Closing (excluding any such Unvested FiscalNote Options and Unvested FiscalNote RSUs to the extent the applicable Earnout RSUs issued with respect to such Unvested FiscalNote Option or Unvested FiscalNote RSU has been forfeited prior to such Triggering Event).

The number of Earnout RSUs issued with respect to each Unvested FiscalNote Option shall be equal to (i) Per Share Earnout Consideration, multiplied by (ii) the aggregate number of FiscalNote Class A common stock underlying the applicable Unvested FiscalNote Option (assuming payment in cash of the exercise price of such Unvested FiscalNote Option), multiplied by (iii) the percentage of the shares of New FiscalNote Class A common stock subject to the related Converted Option that are unvested as of the Triggering Event. The number of Earnout RSUs issued with respect to each Unvested FiscalNote RSU shall be equal to the (i) Per Share Earnout Consideration, multiplied by (ii) the aggregate number of FiscalNote Class A common stock underlying the applicable Unvested FiscalNote RSU, multiplied by (iii) the percentage of the shares of New FiscalNote Class A common stock subject to the related Converted RSU that are unvested as of the Triggering Event.

Shares of New FiscalNote Class B common stock will have the same economic terms as shares of New FiscalNote Class A common stock, except that shares of New FiscalNote Class A common stock will have one vote per share and shares of New FiscalNote Class B common stock will have twenty-five (25) votes per share. FiscalNote stockholders, which will be FiscalNote Co-Founders Timothy (Tim) Hwang and Gerald Yao, holding New FiscalNote Class B common stock will hold approximately 6.4% of the common stock of New FiscalNote outstanding immediately following the consummation of the Business Combination, representing approximately 63.1% of the voting power in New FiscalNote. Each share of New FiscalNote Class B common stock will convert into one share of New FiscalNote Class A common stock (i) at the