Suppose that when the mouse button is pressed and a click is heard, then it is time t0.
And when the key is released (and a click is heard), then it is time t1.
The time instant t1 (click-click) should be longer than it is now.
At the age of 89, the fingers are no longer very supple, although the head still works well.
Can libinput be removed or replaced with another program (= old gui)?
As far as I can see, it does not matter how long the mouse key is down during clicking. When I press, leave it there for seconds and then release, the click action functions as expected.
The problem might be that the mouse is moved between the press and the release. That then results in either nothing happens or maybe moving objects.
Double click is a separate event. Generally action happens on the mouse button up event. In Linux the default is single click so any action happens on the mouse up event no matter how long you hold down the button as long as you are over the control. Unless you turn on the double click option then the timing between clicks is important to trigger the double click event. In Windows double click is the default.
If this is true then the comments you made in post #5 are applicable, and there should be no issue with a slow “release” from a button click, unless as you also describe the mouse is moved while the left mouse button is down.
Just for the record,
I made the update from LEAP 15.1 (with everything working fine) to 15.2 so far with a some problems.
And one thing I noticed was that the scroll wheel acceleration was huge.
And on systemsettings5 -> hardware -> pointing devices -> mouse there was only one single options panel window.
Indeed KDE forums does mention this is due to the lack of evdev mouse options.
so I simply added the /etc/X11/xorg.conf.d the file 80-mouse.conf mentioned in this thread,
And now all work just fine there was no need to even set anything since the mouse started to work as it used to before only by loging out an restarting X11 then re-login on the Plasma5 session.
So everyone with the same problem this is the solution.
This has nothing to do with the OPs problem (as reported), which was not about mouse speed or acceleration behaviour. Best to post to our ‘Unreviewed How To and FAQ’ forum with this kind of thing. I’m not so sure that it represents some universal solution in any case.