I have a Razer Abyssus 1800 mouse, and can't change the mouse sensitivity in Kubuntu 16.04. These are my settings:
If you want to change the mouse sensitivity, this still works in KDE neon with Plasma 5.9. It's just like Kubuntu, except you get the latest KDE software. You don't need to use the libinput instruction the author added for Fedora users. https://patrickmn.com/aside/lowering-gaming-mouse-sensitivity-in-ubuntu-9-10/
xinput in a terminal to find your device. The author of the article used
xinput --list --short, but I get the same result without the options.
A value higher than 1 lowers sensitivity. 2 is 1/2 sensitivity.
xinput --set-prop "Your device name in quotes" "Device Accel Constant Deceleration" 2
You can see your settings here.
xinput --list-props "Your device name in quotes"