At least on Debian Sid Mypaint 1.2.0 is broken on Huion H610 Pro.
UPDATE: See Below:
The Huion works in Inkscape, Gimp 2.8.16, but the pressure freehand and the inking outputs clear to the screen. Every other output works.
Oddly, or not, the same behavior in Krita 3.x on Linux. Works great on OS X because OS X has proper support.
So what library is MyPaint sharing with Krita that deals with pressure sensitive brush that is not being shared with Gimp or Inkscape?
UPDATE: GNOME 3.22
After a painful backup and clean reinstall of Debian from the freshly minted Debian 8.6 DVDs I then updated the entire system to use Debian Sid and GNOME 3.22/KDE 5. Several hours later and slowly getting all aspects to play ball [I would recommend for the novice to wait until PERL 5.24 is fully baked into Debian before attempting] I noticed a few Xorg packages were removed: namely VMMOUSE.
You'll notice that there is exactly 1 reference to the Pen and Control. The scribbling is success. So, no DIGI drivers needed. Just straight evdev out of the box and libinput to the latest Xorg in Debian Sid, which upon updating dropped the vmmouse driver modesetting driver.
RECOMMENDATION: HUION 610 Pro fully works. I can work on customizing the Control settings later as I am just happy I got it to just work.