Sometimes it’s pretty easy …
The solution is to set the proxy directives directly on the IP address of the Docker container
So for example …
Server name checkmk.My-FQDN
ProxyAddHeaders Off
ProxyPreserveHost On
ProxyPassMatch (. *) (\ / Websocket) $ “ws: // <IP-Check_MK-Docker-Container>: 5000 / cmk / check_mk / $ 1”
ProxyPass “/” “http: // <IP-Check_MK-Docker-Container>: 5000 /”
ProxyPassReverse “/” “http: // <IP-Check_MK-Docker-Container>: 5000 /”
… and it works!