It's much improved by 19.10 on my machine, which IIRC went from libinput 1.12 to 1.14. The thumb detection (which was wrong just often enough to be torture) in Pop 19.04 is pretty solid in 19.10.

But then again I don't use anything fancy beyond one- or two-finger gestures. If you want all the fancy gestures, I can't really say much about that.