A couple of things.
The listing you give is for the core pointer, there should be entries for the tablet as well that might show some strangeness, but I would leave that for the moment apart from looking in the Edit menu -> Input Devices where there should be something like this screenshot: https://i.imgur.com/Z5e1HaQ.jpg
What it does show is the 'bluetooth mouse' Assuming the tablet is regular USB. Have you tried using a regular USB mouse in place of the bluetooth? The problem might be hardware related.
For Ubuntu (and associated such as LinuxMint) you need to add a PPA. That gives Gimp 2.8.22
see: https://launchpad.net/~otto-meier/+archive/ubuntu/gimp there is information on the page for enabling it.
The listing you give is for the core pointer, there should be entries for the tablet as well that might show some strangeness, but I would leave that for the moment apart from looking in the Edit menu -> Input Devices where there should be something like this screenshot: https://i.imgur.com/Z5e1HaQ.jpg
What it does show is the 'bluetooth mouse' Assuming the tablet is regular USB. Have you tried using a regular USB mouse in place of the bluetooth? The problem might be hardware related.
For Ubuntu (and associated such as LinuxMint) you need to add a PPA. That gives Gimp 2.8.22
see: https://launchpad.net/~otto-meier/+archive/ubuntu/gimp there is information on the page for enabling it.