Everything about Linux
RULES
Be nice to each other.
No memes or pictures of Linux in the wild.
As the others said, windowed mode at your desired resolution, fullscreen at your desired resolution, or if neither work, gamescope.
Gamescope will make the game believe the display is a particular resolution and force it to run that way regardless of the actual hardware.
Doing this in reverse all the time. Stretching games on my triple head setup to full size. It's the same principle. If the game doesn't offer it kill it with gamescope, Wine virtual desktop or if nothing helps a completely virtual display that overlays your current:
https://beko.famkos.net/2021/05/31/extreme-multihead-for-gaming-on-linux-pc/
For some editing the config files directly works wonders. Looking at you Unity!
I don't recomend Ultrawide Displays for gaming on linux. Get it and you,LL SUFFER (spoky voice).. The EDID of my UW display (predator) is horrible .. like.. uw 1440p or 768p and nothing in between..
Tbh theres have been a couple of years since the last time I tried and people says that gamescope does the trick but I didn't tried.. but believe me that It was a real pain in the passt to avoid res stretching.
Just set the game to full screen 2560x1440. The monitor does the right thing.
No it won't. Source: me suffering during years gaming on Linux on UW display.
Works for me. I have a Dell UW.
What are your EDID resolutions? Is there real display scaling available ? Mine Takes the whole monitor no matter what. Maybe yours was designed by a sane engineer.