Some help with virtual desktop resolution please


I am trying to run a game with lutris. My desktop is set to 4k resolution. The game does not offer this resolution however. So I want to play the game in a window that has a resolution of 1920x1200. The game however only supports 800x600.

So when the game is started the virtual desktop scales down to 800x600, even though it is set to 1920x1200. What I want to achieve is that the virtual desktop stays at its resolution of 1920x1200 and the game instead get’s streched to this size, no matter if it just supports 800x600.

How can I make this work?

Any help is appreciated.