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 datefield in the JSON user database (see second item under “Other changes”).The implementation of this field was prompted by age-verification or -attestation laws.
Writeup by @pglpm@lemmy.ca
Your instance (if it’s anything like lemmy.blahaj.zone) likely turned off downvotes which (I’d guess) is why you don’t see a button for it.