> lack of backups if a device is lost/broken

That's not accurate. Bitwarden syncs passkeys across all my devices including both mobile/desktop (iOS/Android/MacOS/Windows/Fedora) using Chrome/Edge/Safari (I haven't tried Firefox).

KeepassXC is an open source alternative for cross-device synced passkeys. Marginally less secure than device bound passkeys but it's seamless and I save so much time now being able to login with one-click everywhere instead of wasting it on arbitrary "let's make sure you're you" MFA nonsense.