A total failure. For some reason the mysql restore refused to work with the sql-file from the old server on the virtualized vm, so had no other option than to move stuff manually.

It will probably take some time until I get it all fixed and corrected.

At least I have all articles inserted into the new server...

I'm thinking the move CentOS 6 and MariaDB 5.5 to Ubuntu 20.04 Server and MySQL 8.0 isn't trivial.
All future OS-upgrades will however be a lot easier than with CentOS...