In Firefox, when you scroll with a touchpad, Firefox acts as if the document has momentum and continues scrolling when you take your fingers off the touchpad. This works particularly poorly on my Logo Yoga 2 Prow notebook because when I remove my fingers from scrolling on the touchpad there is some kind of jerky signal sent. As a result, considerable momentum is supplied. After too much research, I found <https://kparal.wordpress.com/2019/10/31/disabling-kinetic-scrolling-in-firefox/> (Kinetic seems an odd word to use for this behaviour.) Solution: about:config set apz.gtk.kinetic_scroll.enabled to false. I guess I could report a problem to the libinput folks. But others have done so, more or less. An nine year old computer model doesn't get much attention.