The libinput people say that they do not do anything about the scrolling speed and that they just pass messages to the compositor so that compositor should make it configurable. In my case on libinput/wayland the edge scrolling on touchpad is extremely fast. So that it would need configuration option to make it working.
Do you have a link to the discussion?
A relevant thing is amount of lines to scroll per click is a QPT setting read from kdeglobals, it doesn't require anything in the compositor - but from what I can tell it's missing in the libinput KCM.
Oh I see I must have it read wrong that it's up to the compositor, so it's only missing in libinput KCM, I'll try to post it there.
Depends. Is your issue only relevant in Qt apps and in places where you're scrolling in "lines" (or rows in a grid view) and generally fine when you're scrolling smoothly per pixel?
duplicate of bug 403843?
Yup. *** This bug has been marked as a duplicate of bug 403843 ***