Collabora not working - Apache Error? Nextcloud 23 error?

I accidentally forgot to update and was on version 20.0.4. Everything worked and I did not think about updating and didn’t know how to anyway. Suddenly Collabora stopped working and I realized I had to fix that. Trying to do that I saw I was way out-of-date and wanted to fix that. Long story short - I had to recreate my entire Nextcloud image and start over from scratch.

I am on this kind of setup on Ubuntu 20.04:

I have managed to get Nextcloud 23 working very well again after reinstallation.

The green checkmark in the Collabora settings in Nextcloud comes up when I enter my document server domain https://collabora.fambook.nu

Trying to open a document I first got the well-known error “failed to load Nextcloud Office”. I have seen a thousand posts on that and how it can be fixed. I have tried everything.

One post suggested downgrading richdocuments. I did that, but couldn’t follow the instructions exactly. It seems to have worked, though. However, after doing that I got another error:

screennotfound

When I enter my domain for the document server in a browser I get the Apache Default Page:

I seem to have setup Apache correctly, is it probable that it is the document server/collabora docker image that doesn’t deliver? Collabora works with the demo-server, but not on my own server - even though nextcloud “green-checks” it.

What could be wrong? Where should I look? Is there a log that might supply more information?

Any help is appreciated.

Thanks!

Cordially,
Martin Book