The fact that I didn't post anything here between 9/17/19 and today might suggest that nothing happened during that time. WRONG! So much has happened that it is not interesting to write down every step.

The problem I faced was my DLNA server, which was installed on the home server with the Serviio app. That no longer worked in the new setup on the restored home server. So I couldn't browse through my collection of movies and TV series anymore. How was I supposed to get Serviio up and running again? I downloaded the available versions but ran into that I don't have a valid license for them. And that while I used to have it.

First tried to restore my then Serviio setup from a backup. That was Serviio 1.9.2. But it didn't help to get that from the backup. I probably just didn't retrieve enough, or it depended too much on the setup it was running in.
It was also impossible to restore a complete backup. After all, it was made in a different environment (different motherboard), so different setup. Moreover, it turned out that the backup had not been constructed smartly. (Sigh...)
Then pulled a trick: version 16.04 of Ubuntu server installed. Then upgraded to an 18.04.1 version. On top of that, I put a complete backup that was made when I was still running on 18.04.03 with the old motherboard. After some fiddling in fstab en netplan , that also wanted to start. And Serviio also became active!
But that didn't solve anything. Most reboots got stuck during boot. It took constant tuning to get a running system... it just didn't work well.

Deep, very deep sigh...

Finally started all over again. Downloaded the latest version of Ubuntu Server 18.04.3 and installed it on the home server. Put Webmin, Usermin and Virtuamin on it. And finally Serviio 2.0. I don't have a valid license for the latter now, but it should allow me to access my files on TV. Serviio 1.9.2 relies on a java setup that is no longer valid on the current version of Ubuntu.
When that all went well, I upgraded the system to release 19.04 and then to 19.10.
And it all works properly now! Just install Drupal and we are where we want to be.

Pffft....