When an application launches a dialog box, such as "choose a file" or "Would you like to perform this action," that dialog box can end up behind another window if another window is clicked. Mandatory dialog boxes such as these should always be presented on top of other windows until it is dismissed. Not having this behavior be default can confuse the user, especially when a dialog box causes an application to enter a wait state until that box is dismissed. Linux/KDE Plasma: Arch Linux (Garuda Linux): Kernel 6.0 (available in About System) KDE Plasma Version: 5.26.1 KDE Frameworks Version: 5.99.0 Qt Version:5.15.6
X11 or wayland session?
This is a bug on both Wayland and X11
At the moment this is by design, but it could conceivably be changed. See also Bug 460730.
I think it is confusing, especially as most programs will become unresponsive when a dialog box is shown (such as polkit or a file picker). Presumably this would be an easy fix as kwin already allows you to keep a window on top of others.