In /etc/xdg/kdeglobals sets [KDE Action Restrictions][$i] action/lock_screen=false and relog. This disables screen locking. The desktop toolbox however still shows the 'Lock Screen' action. The action is defunct and not doing anything though. The action should not be shown when lock_screen is being restricted.
Git commit 4932c6e2cbc949b6566d0672dfd1ba15ba944d2d by Kai Uwe Broulik. Committed on 23/04/2018 at 13:12. Pushed by broulik into branch 'Plasma/5.12'. [Power Management Engine] Fix kiosk restriction for lockscreen It is action/lock_screen according to documentation. FIXED-IN: 5.12.5 Differential Revision: https://phabricator.kde.org/D12375 M +1 -1 dataengines/powermanagement/powermanagementengine.cpp https://commits.kde.org/plasma-workspace/4932c6e2cbc949b6566d0672dfd1ba15ba944d2d