I was very sad when KDE reintroduced the concept of “primary screen”.
It used to just be the current screen, which meant that when I wanted to game or watch something on my projector, I just dragged steam or the folder with movies to the projector screen, then launched whatever I wanted, and it appeared on the screen I wanted it on.
Now I have to jerryrig kwin and a custom steam-in-gamescope Launcher to have games launch there. As a side effect, steam thinks my PC is a steam deck and therefore can’t be exited from inside of it, I have to right click the tray icon.
Horribly kludgy compared to “click launch game button on screen x, game opens on screen x”