I am pretty confused about this guide. Passkeys aka FIDO2 aka webauthn seems to not be supported in Vanadium.
Plugging in a Nitrokey 3a-mini displays a prompt to open an app, openkeychain is supported for storing GPG keys, thats it.
The Nitrokey 3's are now FIDO2 compliant.
KeepassDX has theoretical support for some type of security key, but not that one.
Tbh using the secure element as an additional passkey on the phone would be great.