Then I’d definitely set up a test system in a VM on your own PC (I.e. not the actual server machines). Even if you don’t want to use Docker, you can set up a complete version of your new server and practice deploying Jellyfin and Plex, and then test accessing it “remotely” to manage it. You can then decide whether switching away from Win11 is worth it.

If you’re not familiar with the process of setting up a linux server then I’d actually suggest Debian instead of OpenSuSe. Looking at the Jellyfin guide for example it specifically covers the steps for installing directly onto a Debian host (while OpenSuSE set up means using the Fedora RPM guide). There are also straight forward guides for setting up a Debian server.

Personally I’m not a fan of Ubuntu (because of Canonical and Snap etc) but there may also be a good choice just because there are so many guides out there for setting up Ubuntu server.