The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

 Names of Reporting Persons

 James Ralph Scapa

 Check the Appropriate Box if a Member of a Group

 (a) ☐  (b) ☐

 SEC Use Only

 Citizenship or Place of Organization

 United States

Number of

Shares  Beneficially 

Owned By

Each

Reporting

Person

With

 Sole Voting Power:

 17,116,566*

 Shared Voting Power:

 0

 Sole Dispositive Power:

 17,116,566*

 Shared Dispositive Power:

 0

 Aggregate Amount Beneficially Owned by Each Reporting Person

 17,116,566*

 Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions):

 ☐

 Percent of Class Represented by Amount in Row (9)

 23.9%*

 Type of Reporting Person

 IN

Based on the information set forth in the Quarterly Report on Form 10-Q of Altair Engineering Inc. (the “Company”) filed with the Securities and Exchange Commission on November 2, 2023, there were 54,627,196 shares of the Company’s Class A common stock, $0.0001 par value per share (the “Class A Common Stock”) outstanding as of October 16, 2023. James Ralph Scapa (“Mr. Scapa”) is the Trustee of the James R. Scapa Declaration of Trust dated March 5, 1987 (the “Scapa Trust”), and the Manager of JRS Investments, LLC (the “JRS LLC” and, collectively with Mr. Scapa and the Scapa Trust, the “Reporting Persons”). As of December 31, 2023 (the “Event Date”), the Reporting Persons may be deemed to beneficially own an aggregate of 17,116,566 shares of Class A Common Stock of the Company. The number of shares of Class A Common Stock reported above includes (i) 10,301,610 shares of Class B common stock, $0.0001 par value per share (the “Class B Common Stock”), of the Company held by the Scapa Trust, (ii) 6,687,182 shares of Class B Common Stock of the Company held by the JRS LLC, (iii) 31,049 shares of Class A Common Stock, (iv) 1,030 shares of Class A Common Stock beneficially owned by Mr. Scapa’s wife and (v) 95,695 shares of Class A Common Stock issuable upon exercise of stock options which are currently exercisable or exercisable within sixty (60) days of the Event Date, and excludes (i) 72,542 shares of Class A Common Stock to be issued pursuant to RSU awards granted to Mr. Scapa with time-based vesting conditions which will not be satisfied upon or within sixty (60) days of the Event Date, (ii) 265 shares of Class A Common Stock to be issued pursuant to RSU awards granted to Mr. Scapa’s wife with time-based vesting conditions which will not be satisfied upon or within sixty (60) days of the Event Date and (iii) 204,000 shares of Class A Common Stock issuable to Mr. Scapa upon exercise of stock options, which will not be exercisable upon or within sixty (60) days of the Event Date. The rights of the holders of Class A Common Stock and Class B Common Stock are identical, except with respect to voting and conversion rights. Each share of Class A Common Stock is entitled to one vote per share and each share of Class B Common Stock is entitled to ten votes per share. Each share of Class B Common Stock is immediately convertible, at the option of the Reporting Persons, into one share of Class A Common Stock and shall automatically convert into Class A Common Stock upon the occurrence of certain events. Please see the Company’s Registration Statement filed with the Securities and Exchange Commission on Form S-1 (File No. 333-220710) for a description of the conversion rights. Thus, as of the Event Date, for purposes of Rule 13d-3 under the Securities Exchange Act of 1934, as amended, the Reporting Persons may be deemed to beneficially own 23.9% of the shares of Class A Common Stock issued and outstanding. The percentage was obtained by dividing (a) the number of shares of Class A Common Stock beneficially owned by the Reporting Persons as set forth in Row 9 by (b) the sum of (i) 54,627,196 shares of Class A Common Stock outstanding as of October 16, 2023, (ii) 16,988,792 shares of Class A Common Stock issuable upon conversion of the Class B Common Stock beneficially owned by the Reporting Persons, and (iii) 95,695 shares of Class A Common Stock issuable upon exercise of stock options that are currently exercisable or that will be exercisable within sixty (60) days of the Event Date.

 Names of Reporting Persons

 James R. Scapa Declaration of Trust dated March 5, 1987

 Check the Appropriate Box if a Member of a Group

 (a) ☐  (b) ☐

 SEC Use Only

 Citizenship or Place of Organization

 United States

Number of

Shares  Beneficially 

Owned By

Each

Reporting

Person

With

 Sole Voting Power:

 10,301,610*

 Shared Voting Power:

 0

 Sole Dispositive Power:

 10,301,610*

 Shared Dispositive Power:

 0

 Aggregate Amount Beneficially Owned by Each Reporting Person

 10,301,610*

 Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions):

 ☐

  Percent of Class Represented by Amount in Row (9)

 15.9%*

 Type of Reporting Person

 OO

Based on the information set forth in the Quarterly Report on Form 10-Q of Altair Engineering Inc. (the “Company”) filed with the Securities and Exchange Commission on November 2, 2023, there were 54,627,196 shares of the Company’s Class A common stock, $0.0001 par value per share (the “Class A Common Stock”) outstanding as of October 16, 2023. James Ralph Scapa (“Mr. Scapa”) is the Trustee of the James R. Scapa Declaration of Trust dated March 5, 1987 (the “Scapa Trust”). As of December 31, 2023 (the “Event Date”), the Scapa Trust may be deemed to beneficially own an aggregate of 10,301,610 shares of Class A Common Stock of the Company. The number of shares of Class A Common Stock reported above includes 10,301,610 shares of Class B common stock, $0.0001 par value per share (the “Class B Common Stock”), of the Company. The rights of the holders of Class A Common Stock and Class B Common Stock are identical, except with respect to voting and conversion rights. Each share of Class A Common Stock is entitled to one vote per share and each share of Class B Common Stock is entitled to ten votes per share. Each share of Class B Common Stock is immediately convertible, at the option of the holder, into one share of Class A Common Stock and shall automatically convert into Class A Common Stock upon the occurrence of certain events. Please see the Company’s Registration Statement filed with the Securities and Exchange Commission on Form S-1 (File No. 333-220710) for a description of the conversion rights. Thus, as of the Event Date, for purposes of Rule 13d-3 under the Securities Exchange Act of 1934, as amended, the Scapa Trust may be deemed to beneficially own 15.9% of the shares of Class A Common Stock issued and outstanding. The percentage was obtained by dividing (a) the number of shares of Class B Common Stock beneficially owned by the Scapa Trust as set forth in Row 9 by (b) the sum of (i) 54,627,196 shares of Class A Common Stock outstanding as of October 16, 2023 and (ii) the 10,301,610 shares of Class A Common Stock issuable upon conversion of the Class B Common Stock beneficially owned by the Scapa Trust.

 Names of Reporting Persons

 JRS Investments, LLC

 Check the Appropriate Box if a Member of a Group

 (a) ☐  (b) ☐

 SEC Use Only

 Citizenship or Place of Organization

 United States

Number of

Shares  Beneficially 

Owned By

Each

Reporting

Person

With

 Sole Voting Power:

 6,687,182*

 Shared Voting Power:

 0

 Sole Dispositive Power:

 6,687,182*

 Shared Dispositive Power:

 0

 Aggregate Amount Beneficially Owned by Each Reporting Person

 6,687,182*

 Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions):

 ☐

  Percent of Class Represented by Amount in Row (9)

 10.9%*

 Type of Reporting Person

 OO

Based on the information set forth in the Quarterly Report on Form 10-Q of Altair Engineering Inc. (the “Company”) filed with the Securities and Exchange Commission on November 2, 2023, there were 54,627,196 shares of the Company’s Class A common stock, $0.0001 par value per share (the “Class A Common Stock”) outstanding as of October 16, 2023. James Ralph Scapa (“Mr. Scapa”) is the Manager of JRS Investments, LLC (the “JRS LLC”). As of December 31, 2023 (the “Event Date”), the JRS LLC may be deemed to beneficially own an aggregate of 6,687,182 shares of Class A Common Stock of the Company. The number of shares of Class A Common Stock reported above includes 6,687,182 shares of Class B common stock, $0.0001 par value per share (the “Class B Common Stock”), of the Company. The rights of the holders of Class A Common Stock and Class B Common Stock are identical, except with respect to voting and conversion rights. Each share of Class A Common Stock is entitled to one vote per share and each share of Class B Common Stock is entitled to ten votes per share. Each share of Class B Common Stock is immediately convertible, at the option of the holder, into one share of Class A Common Stock and shall automatically convert into Class A Common Stock upon the occurrence of certain events. Please see the Company’s Registration Statement filed with the Securities and Exchange Commission on Form S-1 (File No. 333-220710) for a description of the conversion rights. Thus, as of the Event Date, for purposes of Rule 13d-3 under the Securities Exchange Act of 1934, as amended, the JRS LLC may be deemed to beneficially own 10.9% of the shares of Class A Common Stock issued and outstanding. The percentage was obtained by dividing (a) the number of shares of Class B Common Stock beneficially owned by the JRS LLC as set forth in Row 9 by (b) the sum of (i) 54,627,196 shares of Class A Common Stock outstanding as of October 16, 2023 and (ii) the 6,687,182 shares of Class A Common Stock issuable upon conversion of the Class B Common Stock beneficially owned by the JRS LLC.

Name Of Issuer:

Name of Person Filing:

Address of Principal Business Office or, if None, Residence:

Citizenship:

Title of Class of Securities:

CUSIP No.:

If This Statement Is Filed Pursuant to Section 240.13d-1(b) or 240.13d-2(b) or (c), check whether the Person Filing is a:

Ownership:

(a)   Amount Beneficially Owned:

(b)   Percent of Class:

(c)   Number of Shares as to which the person has:

(i) Sole power to vote or to direct the vote:

(ii)  Shared power to vote or to direct the vote

(iii)  Sole power to dispose or to direct the disposition of:

(iv) Shared power to dispose or to direct the disposition of

(a)   Amount Beneficially Owned:

(b)   Percent of Class:

(c)   Number of Shares as to which the person has:

(i) Sole power to vote or to direct the vote:

(ii)  Shared power to vote or to direct the vote

(iii)  Sole power to dispose or to direct the disposition of:

(iv) Shared power to dispose or to direct the disposition of

(a)   Amount Beneficially Owned:

(b)   Percent of Class:

(c)   Number of Shares as to which the person has:

(i) Sole power to vote or to direct the vote:

(ii)  Shared power to vote or to direct the vote

(iii)  Sole power to dispose or to direct the disposition of:

(iv) Shared power to dispose or to direct the disposition of

This report on Schedule 13G, is being jointly filed by (i) the Scapa Trust, (ii) the JRS LLC, and (iii) Mr. Scapa, individually and as the Trustee of the Scapa Trust and the Manager of the JRS LLC.

Ownership of Five Percent or Less of a Class

Ownership of More Than Five Percent on Behalf of Another Person

Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person

Identification and Classification of Members of the Group

Notice of Dissolution of Group

Certification

A power of attorney was previously filed with the Commission and is incorporated herein by reference to Exhibits 99.2, 99.3 and 99.4 to the Schedule 13G filed by James Ralph Scapa on February 14, 2018.

Exhibit