When I first installed KDE in Tumbleweed, the touchscreen scrolled, not highlighted. Haven’t tried Chrome/ium to see if that behavior is specific to Firefox, but it appears so. I have installed Fedora 42 with Cosmic DE, and the same version of Firefox (139.0.4) responds to touch as an attempt to scroll up/down like a tablet.
Any suggestions are appreciated. As mentioned it was initially behaving as desired, e.g., scrolling, but now it just highlights the text unless I use the very slender scroll bar at the far right.