I wish I made something advanced, but anyways. This thing helped me a lot, so I'll share it. I hacked a Behringer X32 Rack mixer board to have physical controls. The idea is it is controllable by OSC, and there is unofficial documentation. So, I made a patch in Pure Data that converted MIDI from Launch Control XL to OSC to control the board. Pure Data was running in headless mode on Raspberry PI and was the only thing running. It was close to a consumer-level product; it loaded up in seconds on power failure and just worked.