I am trying to set up collabora online on an lxc container for my nextcloud in another lxc container.
Both reside behind an nginx reverse-proxy that also does tls-termination in a third lxc container. I installed the native debian 9 packages and configure collabora as explained here: https://morph027.gitlab.io/post/collabora-online-without-docker/ and set up the nginx reverseproxy following the official guide (of course replacing localhost with the local network ip of the the collabora container).
The discovery in the nextcloud app seems to be working as it accepts the url, however if i open a document in nextcloud, it shows a blank page. Completely blank not even the collabora ui.
If i look into web developer toolbar, there is just a 500 Internal server error code returned.
I made sure that the reverse proxy is not the problem, as it shows 502 Bad Gateway if the proxy is turned of, so this has to be a misconfiguration on the collabora container. But what did i miss?