some password managers can pretend to be a passkey. but I don't use them because it requires finicky brittle configuration (and docs lookup whenever you want to redo it).

if passkeys had a simple text challenge response text option it would be fine, you would basically be using something like PGP logins. and would be easy to implement in a password manager interface.

as a result, I have zero interest in passkeys. a pity as it could have been useful (cold storage password manger + physical passkey). you can never trust any service to honor "backup" login options, got burned once for "suspicious activity". that is, if you lose a login option (passkey is lost) they can demand it in the future to "verify".