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 Though stock GNOME is horendous to use because the way it uses dock makes no sense. I like Ubuntu or Manjaro "interpretation" of it. I know you can install Dash to Dock, but I prefer if OS already has that without me having to fiddle with it.