For those interested on the question of age verification and GNU/Linux: be aware that Systemd v261-rc1 was recently released. It now implements an optional birth date field in the JSON user database (see second item under “Other changes”).
The implementation of this field was prompted by age-verification or -attestation laws.
Well I mean if you add an age field now and pretend it works you might get in front of laws which would require a shittier version. Now they can say “we have age verification”.