Keycloak's Yubikey passkeys don't seem to be passkeys. Given that passkeys on a yubikey is a "FIDO2 discoverable residential key", it requires an entry to be visible when doing ykman fido credentials list. There are entries on mine for Github, Google, Amazon, etc. But not Keycloak. It seems it just registers it as traditional U2F / webauthn.

This seems worthy of a bug report?

Also, on a Windows 11 PC with TPM, you first have to cancel a couple of popups before it finally gets to the Yubikey. Also not really a great experience.