Ok. Scratch a lot of what I said about the mappings. Since I was away from home, I didn’t have my real driver and real device to look at. I would suggest that you use the MIDI log page on the Zynthian web interface to view in real-time what MIDI CC channels things are coming in on, etc. After coming back and looking at things, I remembered that the Generic Preset that I ended up settling on had a very strange layout for the faders, knobs and buttons. So, since I don’t have an MPK49 here to test with, I could only rely on what I can find on the internet (which I don’t expect to be reliable after my experience with the MPK249. Since I think that you will get a lot farther faster if you can gather real data off the device as you use it, I would suggest that you do that. If, at that point, you’d like my assistance getting it working, I would be happy to assist.
Gather as much information as you can about the pads as well. In my configuration, all of the pads on that preset are on MIDI channel 10, That was one of the key reasons for choosing to use this preset over some others, because it allows segmenting all of the pads into one channel that can be unrouted from chains, and treated only as a looping control mechanism. I suspect that given the layout of your pads, the mappings are going to be wildly different.
So, please gather as much of that information as you can, which I think will get you 95% of the way to having most of it working. I am happy to help if you run into other problems, limited, of course, by not having the device here to test. Good luck.