Where does it explicitly mention operating systems?
Ok, so you’ll say that it just applies to operating systems even though it’s not explicitly mentioned. Show me where the ADA has been used successfully in a lawsuit against an OS developer for the construction of their OS. I’ll wait!
(e) (1) “Covered application store” means a publicly available internet website, software application, online service, or platform that distributes and facilitates the download of applications from third-party developers to users of a computer, a mobile device, or any other general purpose computing that can access a covered application store or can download an application.
(2) “Covered application store” does not mean an online service or platform that distributes extensions, plug-ins, add-ons, or other software applications that run exclusively within a separate host application.
(f) “Developer” means a person that owns, maintains, or controls an application.
(g) “Operating system provider” means a person or entity that develops, licenses, or controls the operating system software on a computer, mobile device, or any other general purpose computing device.
...
1798.501. (a) An operating system provider shall do all of the following:
(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:
&c.
So yes, OSes are mentioned directly. The lawsuits will only come after it goes into effect.