Just got a Huion H640P. π I am happy to report it works great on Linux Mint 20 even without drivers. However, using the #DIGImend drivers (https://digimend.github.io) allowed Linux Mint to recognize it as a graphics tablet, which allowed me to further configure it using its GUI tool.
Unfortunately, I still don't see a way to configure the programmable keys on the tablet itself through the GUI. I have to use the terminal for that. Other than that, it's a real delight. π π