I’ve got an Akai MPK25 (little sister to the MPK61), and it works perfectly on Linux.
The drum pads work perfectly, although I applied the fix detailed on Youtube to make them more responsive - nothing to do with Linux, however.
As an aside, I use the keyboard with other apps outside our beloved Renoise - and have never had a problem. Even assigning buttons to keys in Windows VSTs under Wine works great.
I haven’t begun to explore the keyboard much beyond its ‘out of the box’ functionality, but everything I’ve played with so far has been fantastic.
Happy to try and help if you come across any problems.
Cheers,
ian