Hello,
It looks like a conflict between xf86-input-synaptics and
xf86-input-libinput.
If xf86-input-synaptics completely superseded by xf86-input-libinput
nowadays?
A maintainer of GNOME control center mentions that synaptics has been
removed from GNOME control center during the development of version
3.20, "because the synaptics X driver isn't developed anymore".
GNOME control center discussion:
https://bugzilla.gnome.org/show_bug.cgi?id=764257
Commit:
mouse: Drop unused synaptics capabilities check
https://git.gnome.org/browse/gnome-control-center/commit/?id=6a86c7e957850b7122a7570abd81f250bc640fe7
I see that we have no report on this problem, I consider leaving the
topic as informative.
Thanks Ludovic