After a bunch of comments pointing out to the fact that my GNOME touch issues were linked to Ubuntu, I did another try, on Fedora, this time, and yeah, it's MUCH better.

I also gave a shot to Plasma Mobile (excellent), and Phosh (less excellent on a big screen):

https://www.youtube.com/watch?v=nCSs4CbxZHk

I was WRONG about Linux & touchscreens: GNOME, Plasma Mobile and Phosh tested

YouTube
@thelinuxEXP the turn-around on this video after you received feedback was kinda bonkers. thanks for clearing this up! for those of us with near-zero interest in tablets in our homes (regardless of hardware or d.e.), it's really helpful to have a clear summary like this.