I had the same symptoms. Try the changes to the code I made in pull request 95. It uses a newer Linux API to register the device, and libinput seems happy with it now, so it works in gimp and inkscape.
Can you describe more precisely your problem : is it on Android or on your
connected Desktop ? (GfxTablet+ only works on Linux Desktops so far …)
Also, you have to compile, install “networktablet+” and “deskwrite”
on the Linux desktop - Have you done so ?