I might have found a solution to KDE Plasma's horrible default touchpad gestures. It's called InputActions, and it's not part of KDE. You have to build it manually from some random 3rd party GitHub repo.
>Heh, GNOME users need to install 3rd party extensions just to make their DE work properly! Not us Plasma chads!
KChuds eternally BTFO.
https://github.com/taj-ny/InputActions