It’s very surprising to me, after remove xserver-xorg-input-wacom (maybe other name in other version) my tablet’s touchscreen’s MultiTouch works in Xorg! Before I do that, MultiTouch works only in Wayland Session.
Could you tell us, what is this tablet (name and type) and how did you install Ubuntu on it? I can’t get my tablets to boot Linux at all. Do you dual boot in it?