I have a 2014 mac mini running Debian (just the CLI although I did use the GUI to set it up just removed the GUI later) and it hosts my Jellyfin and *arr stack. I just installed rEFInd on it and booted it to a USB drive with Debian on it, knowing it worked enough to do that much I ran some tests, every thing excluding the HDD said it was working ok. So I stuck an external drive to it and installed Debian on it. In a few weeks I am hoping to inherate a 2018 Mac mini but as I understand it it will be a little more difficult because of a T2 chip or something, not impossible just not as easy.