I use KDE and I have this problem. Similarly when I switch vterms (I have separate X11-Sessions for my personal and my work-from-home user account), I can brief

I use KDE and I have this problem. Similarly when I switch vterms (I have separate X11-Sessions for my personal and my work-from-home user account), I can briefly see the content of the session that I switched away from (without having locked it) before the lockscreen comes up.