How to use Gamescope

[U+48]

Before I migrated from Windows to Linux, I used a program to upscale game windows called Magpie. Trying to find an alternative for Linux, and I found Gamescope, which is apparently built into Steam… I think. But when I try to use it, it doesn't work. I'm using

"gamescope -h 480 -w 640 -H 1080 -W 1920 -S integer"

in the Launch Options for UNDERTALE (GOG Games), but it just doesn't work?

[slickdog75]

Have you added " -- %command%" to the end of the command?

eg: "gamescope -h 480 -w 640 -H 1080 -W 1920 -S integer -- %command%"

https://github.com/ValveSoftware/gamescope?tab=readme-ov-file#examples

[U+48]

-- %command%

does nothing

It doesn't work for Non-Steam games does it?