Note: This worked all right in Kubuntu 18.04 LTS.
I am using a fresh install of Kubuntu 18.10, with the default plasma version that comes with it: 5.13.5.
The option in System Settings keeps getting reverted every few minutes. On visiting again, it shows a message meaning that the "Options visible are different from those in effect" and on refreshing, option gets unchecked. Screenshot:
xinput method, xinput --set-button-map 13 1 2 3 5 4 6 7,found in some answers is causing unreliable effect, i.e. some of the apps start working reverse while some work inverted of inverted (i.e. original default).
Xorg method of setting Option "NaturalScrolling" "on" is having no effect.
Is there a reliable, permanent method of setting "natural scrolling" in Kubuntu 18.10?
Update 1: I have seen that some of the options like X config work on boot, but at some point stop working randomly. I have not been able to pinpoint what causes it though (yet).
Update 2: Confirming that my natural scrolling option keeps getting reverted!
This looks like a bug specifically in the plasma version in question, 5.13.5, which ships by default with Kubuntu 18.10. I installed 5.14 and this seems to have resolved itself.