Public service announcement
In which I did not check the full nature of the fix
An update on
The details are in the following and the referenced links,
The short explanation is that, yes,
libinput was installed, and yes there were some
.conf files in
But not with the right content.
The full installation line is
sudo apt-get install xserver-xorg-input-libinput xserver-xorg-core
And this creates simpler and different
.conf files which do the trick, as far as I can see.