We got into this mess because people wanted Facebook to have age verification, and MZ decided to push the responsibility on to OSes. The result looks to me like Facebook will ban access from non-approved OSes like Linux. Android will still be allowed, GrapheneOS probably not.
TBH, OS based parental filters are the optimal solution here, especially if implemented in a proper way. Kids don't buy phones and computers, parents do. When setting up the account for the first time, the parents could set the account to be an "underage one", all the apps, browsers, etc., would get the USER_IS_UNDERAGE flag and filter content according to that. No need for every site to ask and verify the age, just…
A parent can change the setting in the OS and have every website and app comply with the OS setting is such a better situation than having to deal with a patchwork of content blockers, social media account settings, and parental controls that leak like a sieve.
Realistically, parents often don’t really have a good way to know what websites and apps you sign up for if you don’t have a crazily locked down device. Parental controls are complicated for non-technical parents and they usually know less than their kids do about the Internet.
A global OS age gate solves a lot of those problems, especially since OS-level controls are way easier to enforce and lock down compared to other methods.