My brother @josean7link is proving NextCloud under Proxmox and Debian. (I think he has not done in NethServer by problems with the proxy of his office)
Some details Collabora / NextCloud the software warns:
We’ll describe how to get Collabora Online running on your server and how to integrate it into your Nextcloud using the docker image Nextcloud and Collabora built.
To install it the following dependencies are required:
A subdomain or a second domain that the Collabora Online server can run on
An Apache server with some enabled modules (NGNIX instructions in a blog here)
A valid SSL certificate for the domain that CollaboraOnline should run on
A valid SSL certificate for your Nextcloud
Note: This guide does NOT cover self-signed certificates. If you use a self-signed certificate then you’re mostly on your own
I hope this can help with anything.