Backup codes, sms phone recovery, alternate recovery email are all there in all of the above.
It's no different to forgetting your password/losing access to your password manager is it? As in i've literally at points lost access with passkeys (i only had 1 at the time) and the way i got back in was very straightforward and no different to losing access to a password manager. I got an email and typed my old password and i got back in and re-setup my passkeys.
The way I assess risk, that's less likely to happen than I am to lose my passkeys.
If I'm using passkeys but can recover my account with SMS, then why am I using passkeys? That sounds like the weak link of security. I'd rather use passwords, where I can understand what the password consists of rather than passkeys if I'm not getting an increase in security.
It's unfortunately not quite the same level of portability as passwords, as I don't think there's any standardized export/import format yet, but these options are significantly better than Apples's and Google's closed ecosystems.