It requires a government-authorised "age verification" "app", but it does not require that it is accessible through standard protocols, so that it can work on a

It requires a government-authorised "age verification" "app", but it does not require that it is accessible through standard protocols, so that it can work on any platform. In practice, the governments will only make it available for Android and iOS. Plus, you cannot have a free OS providing "attestation"; "attestation" is incompatible with root access and modifying the OS.