This is very interesting. I am going to try the live distribution of GrandOrgue to see how it works under Linux. In the past when I've tried to work with Linux I've not found my command line skills up to the task, and getting sound cards etc. that work properly hasn't been easy either. I do use Linux on Raspberry Pis with mpd as music clients to deliver music from a central server.
Right now I'm running Mac OS on an old Mac Pro, and it seems to work fine except for some RTMidi error messages. I'm going to start with the internal sound capability, but my goal is to get to a multi-channel system once I get the basics right.
I did my own MIDI boards using Arduino Leonardo and Pro Micro boards, because they output MIDI over USB, which is less interfacing effort for me, and a single cable carries power and data, so internal control wiring is just four USB cables.
I haven't yet had the chance to do much with the organ sample sets, because I'm still building the organ (one manual and the pedals implemented so far). I'm looking forward to that stage in the process.