This really ought to be a linked topic reply to this post, but I don’t seem to be able to do that right now.
https://community.mypaint.org/t/tilt-does-not-work/515
It looks like tilt is broken on Windows. MyPaint’s use of tilt is wholly dependent on GDK reporting tilt to it correctly (or at all).
GDK is a lib we don’t directly control. However it’s open source and you can send patches to its developers. It is possible that the init-time test in gdk/win32/gdkdevicemanager-win32.c is being too strict about letting tilt through.
It’s trying to interface with an ugly proprietary thing called WINTAB.dll, which is basically a bit of the tablet driver that presents a supposedly fairly uniform programming API for tablets, albeit an old 16-bit era one. Most manufacturers have chosen to support it, which is good until you realize that things like MyPaint will only really support one of your tablets at a time unless your drivers support a range of tablets (Wacom’s seem to, other manufacturers I’m not so sure about).
There’s a worrying comment in the GDK code’s decode_tilt(). It would be good if someone with time could look into this area too:
/* As I don't have a tilt-sensing tablet,
* I cannot test this code.
*/
We have a ton of information about making debug builds of GTK/GDK on our wiki right now: Debugging […] on Windows. If you’re trying to get tilting tablets working again, you may want to set DEBUG_WINTAB in the compiler when you build 
