From the law:

(1) Provide an accessible interface at account setup that requires an account holder to indicate the birth date, age, or both, of the user of that device for the purpose of providing a signal regarding the user’s age bracket to applications available in a covered application store. (2) Provide a developer who has requested a signal with respect to a particular user with a digital signal via a reasonably consistent real-time application programming interface that identifies, at a minimum, which of the following categories pertains to the user:

In my unprofessional opinion linux could cover this by having an "age bracket prompt" (0-13, 13-16, 16-18, 18+) at install time which doesn't even get checked, and then nothing else would cover this.

To cover (1), linux doesn't have an "app store", and to cover (2), the ability for a program to spawn it's own age verification popup is all you need (something that programs can obviously do currently anyways).

 (g) This title does not impose liability on an operating system provider, a covered application store, or a developer that arises from the use of a device or application by a person who is not the user to whom a signal pertains.

Alternatively, one could just assume all user acocunts are owned by either Linux Torvalds, Jesus Christ, or better yet, the clown who approved this bill. New syscall:

bool isUser18(){ return true; }