Kyriakos Terzopoulos writes:
ImportError: cannot import name 'path' from 'importlib_resources'
Try putting the error message into Google with "" around it. (This is generic advice for the future, obviously I already know what it is and will tell you. :-)
This is a known issue where Python changed some APIs that Mailman uses. Discussion is here: https://gitlab.com/mailman/mailman/-/issues/1093 There's a simple patch to requirements.txt at the end of the comments. Edit it, and delete and reinstall the mailman package, it will take 10 minures. If you're familiar with Python and pip you can also force remove that package, then reinstall with the additional version constraint.
In general would it be better or/and easier to set this up on a new machine in my Hetzner cloud e.g. on Debian which seems to have packages of mailman available?
That depends. Do you want to get your Mailman help from Debian (the answer is "NO!!"[1] unless you mostly expect to need no help -- that probably works for 70% of Debian + Mailman users) or from us? Unless your use case is exactly what the distro maintainer envisions, you will occasionally run into issues that are impossible for them to figure out, and rather expensive for us to help you with since they depend on old and modified versions. We strongly prefer you use a venv install, and if Mailman is at all important to your site's mission, you probably will too.
Footnotes: [1] At least for servers, I prefer Debian myself. Distros are the best thing since sliced bread. But Mailman is still a relatively fast-moving target[2] and none of the distros keeps up.
[2] In part because Gmail, Yahoo!, and O365 hate mailing lists, almost as much as the spammers hate us, and we keep tweaking things to deal with both kinds of Internet mischief.