After Big Sur update, LG Ultrafine 4K external monitor no longer in high resolution

I had all kinds of problems as well, with 11.1. I have the same setup but with a 43" 4k monitor from LG. Every time I disconnected and reconnected the USBC cable, the maximum resolution would drop until I was only able to run it at 800x600. I tried to reboot and I did an NVRAM / PRAM reset but it didn't make any difference.

Finally, I was able to fix it by connecting the same monitor through another input via HDMI (via a USBC hub). The resolution increased immediately and then when I plugged the USBC cable in directly it started working as well through that input.

I just upgraded to the 11.2 public beta and the issue has been resolved. Now let's see what new issues have been introduced...

I posted in a another thread that the solution for me was a third party utility from https://www.madrau.com/ called ScreenResX. Shareware free to use for ten days.

Of course HDMI was also working for me but only at 30Hz.

Are you sure you don't have Mirroring enabled in Displays preference? Your settings are what I get if I mirror my 4K LG and 1080p TV display.

Make sure you choose one of the resolutions flagged HiDPI or something similar. I noticed blurry text as well until I did that.

I'm running Big Sur (11.0.1) on a 2018 Mac mini with a LG Ultrafine 4K and getting full resolution.

Graphics/Displays in System Information (Option click at top-left of screen) shows:

"LG UltraFine:

Resolution: 3840 x 2160 (2160p/4K UHD 1 - Ultra High Definition)

UI Looks like: 1920 x 1080 @ 60Hz

Framebuffer Depth: 30-Bit Color (ARGB2101010)"

What does it show on your system?

I'm using a Thunderbolt 3 cable, but you should be able to get 4K with just a USB-C cable. (Maybe you have the older version that was USB-C only, not Thunderbolt 3.)

This is really disappointing and unacceptable that Apple hasn't released any update on Big Sur for fixing this annoying issue. I have decided to install Windows on an external solid state drive, and run my computer from there. The external monitors and everything in general works fine, as it suppose to. Very time consuming procedure, specially because I had to reinstall all the software I use e.g. Adobe and Microsoft Office, but fortunately it's been done from the cloud. BTW, my MBP 16 inch, 2019 behaves amazingly on Windows, QUITE FAST!.

Hoping to not get used to this temporary solution, and that Apple finally fixes such pain in the ***. I'm pretty sure the same is happening to MANY Mac customers. APPLE SHOULD SAY SOMETHING, at least to apologize!

I have the same problem on the LG HDR 4K 32UD99-W monitor. On macOS 11.0.1 it worked fine. After updating to 11.1 it broke already. A few days ago I installed 11.2 RC and I thought it was ok too but after rebooting the problem returned. Yesterday, Apple released macOS 11.2 RC2, but this build doesn't fix the problem either. I had to return to Catalina to work. Hey Apple, do something about it !!

I have same problem with BenQ EW3270U 4k monitor, it shows only 1080p with usb-c, but ok with HDMI to show 4k.

I have just incurred this same issue on my MBP 16" and LG 4K with Big Sur 11.1

It is all of sudden maxing out at 720p. Annoying as I seem to be unable to resolve this using any of the suggested solutions...

Just an update that ScreenResX solution stopped working for me. I'm stuck with my HDMI connection at 30Hz if I want any sort of high resolution. It's been a month, Apple has not done anything about it afaict.

You must mean this screen. Sorry those are all the resolution options I get.