Thanks to the XFCE desktop.
Just did some quick doodling in Krita and it works just fine.
Unity was ment for tablets too.
And mobile phones, so the mouse pointer disappears when using a tablet. Only thing is that in this case it is not a touch screen, but a drawing tablet. Guess the unity Ubuntu desktop went wrong there, same for the Gnome version in 16.04.
Solution was simple, install the XFCE desktop enviroment and hey presto, the drawing tablet works and still shows the mouse pointer. Anyway typing: sudo apt-get install xfce in the terminal was all it took. Just fiddled about a bit with that one, because it can be adjusted in many ways. And finally did some quick drawing in the amazing free open source drawing software Krita.
Think I do even prefer the XFCE interface over the Unity one...
Have a great one!
Some quick doodlin' in Krita.

image cc-by-sa @oaldamster