Hello,
I have updated to KUbuntu 18.04 with KDE 5.44.0 and Plasma 5.12.6 from Kubuntu 16.04
One of the changes between versions in KDE/Plasma which I want to disable is that keyboard layout now is memorized for each application and persist even after reboot. Lets say I open Kate editor, change keyboard layout from English to German and closed it. Next time I open Kate it will automatically change my layout to German in Kate window. It looks like KDE/Plasma saves somewhere last keyboard layout used for each application. However it is completely uncomfortable for me. So my question - is it possible to disable such behavior and change keyboard layout only for currently running application (In my Keyboard Hardware and Layout I have Switching Policy set to Application)? In KUbuntu 16.04 (I can't say which KDE/Plasma goes with it by default) there was no such behavior and newly started applications had default keyboard layout.