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.
Did you ignore the comment in the github where it, and I quote “Stores the user’s birth date for age verification, as required by recent laws in California (AB-1043), Colorado (SB26-051), Brazil (Lei 15.211/2025), etc.”. Yes it is optional NOW, but this is in preparation of laws that make it legally Mandatory. Don’t down play this.