Item 4 of the Original Schedule 13D is hereby amended and supplemented with the following: On July 19, 2026, Atlas GREE Investment Holdco LLC, a Delaware limited liability company and an affiliate of the Reporting Persons ("Purchaser"), entered into a subscription agreement (the "Subscription Agreement") with the Issuer, pursuant to which Purchaser has agreed to purchase, 2,923,976 shares (the "Shares") of the Issuer's Class A Common Stock, par value $0.0001 per share (the "Class A Common Stock"), at a price per share of $1.71, for an aggregate purchase price of $5,000,000, in a private placement (the "Private Placement"). The closing of the Private Placement is subject to the satisfaction or waiver of certain customary conditions. In connection with the closing of the Private Placement, pursuant to an Investor Rights Agreement to be entered into between the Issuer and Purchaser (or its permitted assigns) (the "Investor Rights Agreement"), the Issuer's board of directors (the "Board") will be reconstituted to consist of ten (10) members, including four (4) directors nominated by Purchaser, and following the receipt of certain regulatory approvals, the size of the Board will be reduced to eight (8) members, including one (1) director nominated by Purchaser and one (1) independent director identified by Purchaser (subject to the consent of the Issuer and another investor). Pursuant to the Investor Rights Agreement, following the Issuer's 2027 annual meeting of stockholders, if Purchaser and its affiliates collectively beneficially own at least 7.5% of the outstanding Class A Common Stock on a fully diluted basis, Purchaser will have the right to nominate two (2) directors and if such ownership is less than 7.5% but at least 5.0%, Purchaser will have the right to nominate one (1) director. In addition, the Investor Rights Agreement will provide Purchaser with certain other rights so long as it maintains certain share ownership thresholds, including the right to have an Atlas director serve on the capital committee of the Board, the right to appoint a non-voting Board observer, a right to purchase its pro rata share of issuances of equity or securities convertible or exchangeable for equity of the Issuer (subject to certain exceptions), and customary registration rights. Under the Investor Rights Agreement Purchaser will also be entitled to project-level acquisition fees and/or promote incentives, to be paid in the form of cash or shares of Class A Common Stock, for certain post-closing services provided to the Issuer, subject to arm's-length terms and required approvals. The foregoing description of the Private Placement, Subscription Agreement and Investor Rights Agreement does not purport to be complete and is qualified in its entirety by reference to the Subscription Agreement, which is filed as Exhibit 99.3 to this Amendment No. 5 and the form of Investor Rights Agreement, which is filed as Exhibit 99.4 to this Amendment No. 5.

The information contained on the cover pages of this Schedule 13D is incorporated by reference. All percentages of Class A Common Stock outstanding contained herein are based on 15,286,349 shares of Class A Common Stock outstanding as of June 30, 2026, according to information provided by the Issuer and assume conversion of all of the 2,680,031 shares of Class B Common Stock beneficially owned by the Reporting Persons in the aggregate. (a) and (b) In the aggregate, the Reporting Persons beneficially own, as of the date hereof, 4,185,382 shares of Class A Common Stock (assuming the conversion of all of the 2,680,031 Shares of Class B Common Stock beneficially owned by the Reporting Persons in the aggregate), representing in the aggregate approximately 23.1% of the outstanding shares of Class A Common Stock (assuming conversion of all of the 2,680,031 Shares of Class B Common Stock beneficially owned by the Reporting Persons in the aggregate). (i) ACR9 has shared voting and dispositive power over 1,920,266 shares of Class B Common Stock and 993,300 shares of Class A Common Stock, representing approximately 16.1% of the outstanding shares of Class A Common Stock on an as-converted basis; (ii) ACR Parallel has shared voting and dispositive power over 689,512 shares of Class B Common Stock and 356,664 shares of Class A Common Stock, representing approximately 5.8% of the outstanding shares of Class A Common Stock on an as-converted basis; (iii) ACR P has shared voting and dispositive power over 70,253 shares of Class B Common Stock and 36,339 shares of Class A Common Stock, representing approximately 0.6% of the outstanding shares of Class A Common Stock on as as-converted basis; (iv) GGH LP has shared voting and dispositive power of 119,048 shares of Class A Common Stock, representing approximately 0.7% of the outstanding shares of Class A Common Stock; (v) ACR GPLP, by virtue of its status as the general partner of each of ACR9, ACR Parallel, ACR P and GGH LP, has shared voting and dispositive power of 1,505,351 shares of Class A Common Stock and 2,680,031 shares of Class B Common Stock, representing in the aggregate approximately 23.1% of the outstanding shares of Class A Common Stock on an as-converted basis; (vi) ACR GP, by virtue of its status as the general partner of ACR GPLP, has shared voting and dispositive power of 1,505,351 shares of Class A Common Stock and 2,680,031 shares of Class B Common Stock, representing in the aggregate approximately 23.1% of the outstanding shares of Class A Common Stock on an as-converted basis; (vii) each of Messrs. Bursky and Fazio, by virtue of his status as a Managing Partner of ACR GP, has shared voting and dispositive power of 1,505,351 shares of Class A Common Stock and 2,680,031 shares of Class B Common Stock, representing in the aggregate approximately 23.1% of the outstanding shares of Class A Common Stock on an as-converted basis.

See above for (a) and (b).

Except as described in Item 3 of Amendment No. 4, the Reporting Persons have not effected any transaction with respect to the Common Stock in the past 60 days.

Not applicable.

Not applicable.

Item 6 of the Original 13D is hereby amended and supplemented to include the following: The information set forth in Item 4 of this Amendment No.5 is incorporated by reference into this Item 6. The description of the Private Placement, Subscription Agreement and Investor Rights Agreement does not purport to be complete and is qualified in its entirety by reference to the Subscription Agreement, which is filed as Exhibit 99.3 to this Amendment No. 5 and the form of Investor Rights Agreement, which is filed as Exhibit 99.4 to this Amendment No. 5.

Exhibit 99.3 - Subscription Agreement, dated as of July 19, 2026, by and between Atlas GREE Investment Holdco LLC and Greenidge Generation Holdings Inc. (incorporated herein by reference to the Subscription Agreement filed as Exhibit 10.2 to the Issuer's Current Report on Form 8-K filed by the Issuer on July 20, 2026 with the Securities and Exchange Commission ). Exhibit 99.4 - Form of Investor Rights Agreement (incorporated herein by reference to the Form of Investor Rights Agreement filed as Exhibit 10.6 to the Issuer's Current Report on Form 8-K filed by the Issuer on July 20, 2026 with the Securities and Exchange Commission).