libwacom is a library to identify Wacom tablets and their model-specific features. It provides easy access to information such as "is this a built-in on-screen tablet", "what is the size of this model", etc.
This functionality is currently used by e.g. GNOME to map built-in tablets to the correct screen.
A common indicator that a device is not supported by libwacom is that it works normally in a GNOME session, but the device is not correctly mapped to the screen.
Use the libwacom-list-local-devices tool to list all local devices recognized by libwacom. If your device is not listed, but it is available as an event device in the kernel (see /proc/bus/input/devices) and in the X session (see xinput list), the device is missing from libwacom's database.
The new device should also be added to the udev rule to ensure all required properties are set When building from source generate an update ruleset with tools/generate-udev-rules after adding the tablet descripton to When updating an installed version of libwacom, add it manually to the existing ruleset (/lib/udev/rules.d/65-libwacom.rules)