For libinput, you can set up MatchIsPointer "yes" Option "AccelProfile" "flat" in Xorg config to achieve mouse input which should result in true untouched 1:1 mouse tracking on screen. It's great that there are now libinput controls in Plasma system settings, however it is unclear how to achieve the same untouched input with it as described above. It's obvious that the "flat" acceleration profile has to be chosen for this. But what about the mouse speed? e.g. 5/10 is way too fast. Could 3/10 be "untouched" speed? On Windows, a setting of 6/11 is "untouched" speed. However, this is far from being logical as well. Maybe it would be clearer if a setting of "0" would be neutral, and the speed slider allowed positive values for increased speed and negative values for reduced speed?
We recently changed the slider to have 11 ticks in Plasma 5.14. So position 6 will correspond to a value of 0.0 and you will have true untouched movement. *** This bug has been marked as a duplicate of bug 395681 ***
Thank you. :) It would be great if you could also check if selected flat profile in mouse settings UI really matches the described libinput config from above. The mouse speed slider behaves quite differently when I use that Xorg config.