I spent months designing a system, exactly like this. An account is not needed, at least for Apple.
Play Integrity could the worst offender here, as it can be leveraged to force a user to have installed the app through the Play Store. Indirectly, requiring a Google account.
Because the attestations will only work on iOS and Google Play integrity attested devices. Meaning Apple and Google accounts required.
A phone is also required then?
This is an assumption, but not confirmed.
I spent months designing a system, exactly like this. An account is not needed, at least for Apple.
Play Integrity could the worst offender here, as it can be leveraged to force a user to have installed the app through the Play Store. Indirectly, requiring a Google account.