Rocketchat behind Apache2 UCS ReverseProxy behind NGINX ReverseProxy


I am running UCS 5 with the official RocketChat Docker Container. So far everything works as expected.
For now I want to create a subdomain for each UCS App (nextcloud, RocketChat, wekan,…). In terms of security I installed a second VM (Ubuntu with NGINX Proxy Manager) which should manage the LetsEncrypt Certifactes and hide all the UCS Stuff I dont want to expose.

I am new to NGINX ReverseProxy Configuration and installed NGINX Proxy Manager to get things done quiet fast. On one point I got stuck: I tried to change the RocketChat URL from to
After some struggle with the correct NGINX config the webbrowser now shows the dark grey page with the loading dots of RocketChat, but no login prompt.

After some testing and research I think there is some misconfiguration with websockets (i enabled this in NGINX Proxy Manager), but I cant figure out how the correct configuration has to be in this type of setting.

Starting Rocketchat with the Standard UCS URL without the NGINX ReverseProxy and Subdomain everything shows up well and fast.

Does anyone can help?

Thank you very much and best regards