WebSocket connections using HTTP/2 and CloudFlare


We've been trying to setup a secure web socket via traffic to a spring Webserver.
The connection is inbound to traefik via HTTP/2. The IngressRoute (HttpRouter) responsible for this endpoint is doing the SSL termination and moving the traffic to a TraefikService with scheme http.
We tried several variants, with middleware which append Headers like "X-Forwarded-Proto: https", but still the furthest we could get is as follows: The Spring WebServer did accept the connection, but it instantly got terminated again and no response was sent to the client.

Am I missing any configuration for the setup as described above?

Thank you & Best Regards,