An obscure graphics tablet works, but maps only a part of the tablet to the entire screen

Question

I have the same problem as described here and here, but with an obscure Chinese tablet Gthang G10, to which I can't find any instructions online, when it comes to using it with Ubuntu. The readme file of the tablet states that it should work out of box for Ubuntu >= 16 (I have Ubuntu 24.04 LTS). The tablet does, indeed, work, but it appears to think that my laptop is a device with vertical screen, and so it uses the right ~40% of of the working area to map the entire screen. For Windows, the tablet has custom drivers which include an app to change the working area, but for Ubuntu there's no such app, and so I have no idea how to change this setting.