Passkey PRF could also be used to backup a nostr nsec to the password manager without users needing to copy/paste private key material.
And since Apple requires turning on 2FA to use passkeys, users get pretty decent security for key backups.
https://support.apple.com/guide/iphone/use-passkeys-to-sign-in-to-websites-and-apps-iphf538ea8d0/ios
nostr:note1vldz25qcwkwzrsnrdjeq8jayawpr5me49du8a97sz2lcljycs2dswrsxtv