Beware that Passkey storage is limited though and I don't think you can reuse one for multiple sites. My Yubikey 5 NFC stores up to 32 and you should have some redundancy if you ever lose it. You also can't export them. I only use passkeys (in Bitwarden) for things I don't care about.

As someone who's looking into possibly getting a YubiKey 5 NFC actually, I would like to ask: if you can't export the entries, if you make a backup of the YubiKey (perhaps with the magic of buying two of them), then how would one ensure redundancy?