If anyone else has this issue, as a temporary solution for anyone else facing this - add to the KDE Window rule that window-position is also forced (separate for title "Friend List" and "Steam"). At least it makes using Steam possible again, although far from perfect (not able to move window at all).
Nothing extracted yet.
Your system information
tar -zcvf ~/Desktop/steam-logs.tar.gz ~/.steam/steam/logs]Please describe your issue in as much detail as possible:
Because applications own titlebars just are bad (does not follow system shortcuts, pin on all desktops etc.) I have system titlebar forced on Steam-windows (kwin_x11 rule) - if this has anything to do with my issue.
After latest update when ever window gains or looses focus (I use focus-follows-mouse), mouse hovers over Store, Library, Community, , enters or exits an opened menu from the "titlebar" etc., the whole window jumps down on screen about the pixel amount of Steams titlebar (or the real system titlebar).
Same happens seemingly with every Steam window - About Steam, Settings, Friend list.
Very very annoying, as trying to click Library becomes a chase to hit it.
Steps for reproducing this issue:
Best fix would be to remove steams subpar titlebar, but in meantime reverting some recent change that repositions window would help.