Intermediate error with Keycloak and WebAuthN using Yubikey in Firefox

[jheidbrink]

I'm doing a password + WebAuthN(Yubikey) login to a Keycloak instance. After letting gopassbridge fill the credentials, Keycloak shows me an error message "Failed to authenticate by the Passkey." and a button "try again". After clicking that button, I'm prompted to touch the Yubikey and login works as expected. When typing the credentials manually, I don't get the intermediate error, but directly get the Yubikey prompt.

This happens on Firefox. Chromium is fine. I already tried clearing cookies and site data and it didn't help.