Xorg logs say the following:
[206016.245] (II) config/udev: Adding input device Network Tablet (/dev/input/mouse1)
[206016.301] (II) config/udev: Adding input device Network Tablet (/dev/input/event18)
[206016.301] (**) Network Tablet: Applying InputClass "evdev tablet catchall"
[206016.301] (**) Network Tablet: Applying InputClass "libinput tablet catchall"
[206016.301] (II) Using input driver 'libinput' for 'Network Tablet'
[206016.301] (**) Network Tablet: always reports core events
[206016.301] (II) event18 - (II) Network Tablet: (II) is tagged by udev as: Tablet
[206016.302] (EE) event18 - (EE) Network Tablet: (EE) libinput bug: device does not meet tablet criteria. Ignoring this device.
[206016.302] (II) event18 - (II) Network Tablet: (II) device is a tablet
[206016.332] (EE) libinput: Network Tablet: Failed to create a device for /dev/input/event18
[206016.332] (EE) PreInit returned 2 for "Network Tablet"
Try the changes to the code I made in pull request 95.
