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.
Is everyone ignoring the direct quote in the orginal post that is referring to laws (California (AB-1043), Colorado (SB26-051), Brazil (Lei 15.211/2025)) that are going to force you to verify your age?
The California law does not require verification. Only attestation.