It's now 2021, and in these glorious days of ray tracing and DLSS technology and such, it's relatively easy for the average gamer to build a rig, grab a 4K display, and be on their merry way. But more ...
On a PC, apps like games and maybe anything else that is using the GPU directly to process the display generally work at fixed resolutions, like 1920x1080 or 216x1440, and when running in full screen ...