Some time ago one of the updates changed the behaviour of the focus
stealing prevention. I have set "focus follows mouse /mouse precedence"
for as long as use kwin. I've also used to set the focus stealing
prevention to "High" so that new windows popping up wouldn't gain focus
automatically when popping up. I've this so I wouldn't inadvertently
type into the new window or dialog that was popping up while I was
thinking I'd write in the editor. After the update that setting is
rendered completely useless: while the popup or new window doesn't get
focus (wanted) it is also forced into the background (not wanted).
This nonsensical behaviour extends even to the applications menu, which
opens behind my active window, rendering it inaccessible. Is there
another setting that controls where new windows are created, I do want
them to open in the foreground, just not get focus until I move the
mouse or Alt-Tab to them. Focus stealing prevention set to "medium"
does open new windows in the foreground, but also gives them immediate
focus (even when the mouse is still over a different window). Setting
"Focus under mouse" also doesn't work the way I want, since it gives
focus to the popup if it happens to pop up under the mouse (focus
stealing prevention doesn't work in this mode, nor does Alt-Tab).