Using libinput and gfxtablet at the same time don’t work. Libinput tries to use networktablet and fails doing so. The cursor doesn’t move and clicking does nothing.
/var/log/Xorg.1.log complains about that it can’t handle the tablet device because of an internal bug.
To solve this you need to add a configuration file, per example
30-gfxtablet.conf, to your
/etc/X11/xorg.conf.d/ with the following:
Section "InputClass" Identifier "evdev tablet catchall" MatchIsTablet "on" MatchDevicePath "/dev/input/event*" Driver "evdev" EndSection