Hi Jogchum,

Sorry, I did not notice that you had a question for me.
<...>
Yes, the steps look roughly correct, possibly except for the part of
shutting down the 10.6.10 server.

As far as the server is concerned, SIGTERM (signal 15) or SIGQUIT
should initiate a shutdown.

I would think that on systemd, the preferred way to start and stop
services would be the following:

systemctl start mariadb
systemctl stop mariadb

Systemd could actually take the role of mysqld_safe.

It could be simplest to start the server directly as "mariadbd" so
that nothing will keep restarting it after you initiated the shutdown.
If you run the process in the foreground, then ctrl-\ should be
SIGQUIT and it should initiate a shutdown.

You'd better check with "pgrep mariadbd" or "pgrep mysqld" that
nothing is running, both before starting and after shutting down the
server.

I will clarify the error message. For 10.3 and 10.4, it will look like this:
https://github.com/MariaDB/server/commit/9ac8be4e2980aa995117147e39ae5b7ad79fc980
Starting with 10.5, it may additionally suggest to use a version not
later than MariaDB 10.4.
Starting with 10.8, it may additionally suggest to use a version not
later than MariaDB 10.7.

With best regards,

Marko Mäkelä