[MilaM]

It's my understanding that passkeys that are created by platform authenticators or password managers can be backed up. That's how replicating your key through iCloud likely works. Hardware keys on the other hand don't support backups by design. You need to enroll multiple keys to have a backup.

> With passkeys, I'd need to set up and authenticate additional devices

This is true, if you don't use a platform authenticator or password manager and only use hardware keys.