Forward Auth Issues

I am having an issue related to forward_auth with Traefik.

As OIDC provider used: Keycloak
As forward_auth proxy used: tried with both Traefik-forward-auth and oauth2-proxy (both not working)
As Ingress controller used: Traefik
Middleware is used to do forward_auth

I am using Ingress kind to be generic, IngressRoute kind never be used.

Can you please provide some guidelines how to solve this issue?

I've been running a forward auth solution for Traefik with Keycloak for a few years now. Perhaps my example repo can help.
All in one package: Traefik + Let’s Encrypt + KeyCloak + Jaeger.