Authentik supports this [1] too, kinda. It seems you can set it up to register you based on a bona fide kerberos auth, and logs you in (maybe? would have to check) with kerberos but seems to keep a parallel synchronized authenticator in its own database for OIDC and "modern" auth. Doesn't seem to embed kerberos-isms as "claims" in OIDC either. Might be awesome if it did? Or terrible, depending on how you look at it.
MIT Kerberos can authenticate using OIDC created token, but in my case I essentially authenticated to Keycloak with HTTP Negotiate with Kerberos, then based on data from LDAP (that was also used by Kerberos) I generated appropriate OIDC token.
[1] https://docs.goauthentik.io/docs/users-sources/sources/proto...