Tapping does not work. I am running this distro from a bootable usb pendrive, on an HP X360 11.6" notebook.
The Input Device utility from the Sparky menu, for some reason, does not work at enabling tapping.
Apparently this was an issue back in 2013 and the fix was to issue the command, synclient TapButton1=1
This fix does work on the notebook I am using, but since I am booting from a bootable usb pendrive, I have to issue this command every time I boot up the distro. :-(
Another possibility is that "Debian testing/unstable has switched from synaptics to libinput|"
Look at the last paragraphs of https://wiki.debian.org/SynapticsTouchpad You are in Stretch.
And another possibility is KDE is in very intense development at the moment in unstable.