LG UltraFine 5K 27Inch Monitor can no longer control the display brightness

I have the same display and have not seen any issues. I use my MBA M1 connected via TB cable and the brightness keys will work but you need to use the control key at the same time. I also use this same monitor with my mac Studio M1 and works great. Have you checked your TB cable and it has to be connected to the monitor port that has the TB symbol and not one the other USB-C ports. I do not use a hub. If you do then try bypassing and connect directly.

Denny_WHL wrote:

1. Since it's release the LG UltraFine 5K 27Inch Monitor has had a host of issues, including:

Flickering when close to Wifi router

2. Severe ghosting

3. Unable to reconnect following sleep

4. Unable to use the speakers

5. Unable to use the webcam and mic

6. Unable to use the USB C ports as a hub

When originally purchased none of these things were any issue and over time these problems appeared one after another. This device was specifically designed by LG in collaboration with Apple to work with the Apple ecosystem and has consistently failed.

Today I have connected my brand new MacBook Pro 14" M2 Max to find that I am now unable to control the display brightness and it is just stuck in a dimly lit state.

Do you say how this connection is made, what cable, directly connected or through some hub/docking..?

ref: https://www.lg.com/us/business/computer-monitors/lg-27md5klb-b

https://www.lg.com/us/support/help-library/lg-monitor-connecting-to-a-mac-CT32009622-20150911473158