Created attachment 111050 [details] demonstration search for "sddm" in apps menu open the search result "login screen (sddm)" maximize and minimize the window click "login screen (sddm)" entry in plasma panel to restore the window Window is redrawed on screen. Watch screencast.
Still reproducible under X11.
cannot reproduce with plasma 5.15 beta. Operating System: Arch Linux KDE Plasma Version: 5.14.90 KDE Frameworks Version: 5.54.0 Qt Version: 5.12.0