4K Display Problem

[anicic.luka]

I'm DESPERATE for a fix for my external 4K monitor. I've followed all the troubleshooting steps provided by Apple and even completely reinstalled macOS Big Sur from scratch! This is seriously hurting my productivity for work.

The funny thing is, my external monitor works perfectly fine when booted in Windows, so it's not a hardware issue.

 

[minik]

I'm DESPERATE for a fix for my external 4K monitor. I've followed all the troubleshooting steps provided by Apple and even completely reinstalled macOS Big Sur from scratch! This is seriously hurting my productivity for work.

The funny thing is, my external monitor works perfectly fine when booted in Windows, so it's not a hardware issue.

What kind of issue? I have the 2020 iMac (w/AMD Radeon Pro 5700 8 GB) and connected to the 27UL850-W via the bundled USB-C cable, no problem under Big Sur 11.2.2

 

[anicic.luka]

What kind of issue? I have the 2020 iMac (w/AMD Radeon Pro 5700 8 GB) and connected to the 27UL850-W via the bundled USB-C cable, no problem under Big Sur 11.2.2

For the external monitor, my max output resolution is 1080p (if I'm lucky). 720p in most cases. Different cables, ports, factory resetting the monitor, along with all the usual SMC/NVRAM resets and erasing my SSD and reinstalling macOS from scratch all haven't worked.

 

[minik]

For the external monitor, my max output resolution is 1080p (if I'm lucky). 720p in most cases. Different cables, ports, factory resetting the monitor, along with all the usual SMC/NVRAM resets and erasing my SSD and reinstalling macOS from scratch all haven't worked.

That's really weird. DisplayPort 1.4? I can get up-to 1:1 resolution but I leave the UI at default for display (1080p).

 

[Fishrrman]

Sounds like it could be "a cable issue" to me.
What Mac are you using?
What monitor do you have (make and model)?
What kind of cable are you connecting with?