So from what I have gathered the window rules work better with Flatpak applications rather than pacman or yay installed ones. A good solution I found for pacman and yay applications starting minimized is to go to autostart, select “see properties” (window icon next to “running”, go to “application” and on arguments add either --start minimized or --minimized. To see what works for each app, start the konsole and type the name of the app and --help (for example “teams-for-linux --help”) and then search if --minimized or --start minimized is listed. Whatever is listed is the thing you’ll have to add on arguments at the start of the already existing sentence if there is something (for teams-for-linux it was %U so add --minimized %U). This will start the app minimized on startup.