HDR and 120HZ Suddenly Not Working

Support and Help
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1

Ubuntu Version: 25.10

Desktop Environment (if applicable): GNOME 49, Wayland

Problem Description: I’m using an LG C4 as my primary display. I’ve been using it for about 9 months with HDR/120Hz and I’ve been happy. Last night after I powered on my system, the TV was no longer switching to HDR and was stuck at 59Hz. Normally it immediately switches to HDR and locks at 120Hz. I am still able to select 120Hz in the settings, but the TV simply doesn’t reflect that. When I turn HDR on the screen becomes de- saturated and the TV doesn’t auto-enable HDR as it should.

Relevant System Information:

  • Mesa Driver: Mesa 25.2.3-1ubuntu1
  • Radeon 9070XT
  • Linux Kernal 6.18.1

What I’ve Tried:

  • Re-seating HDMI cable on both sides.
  • Checking performance on Windows (dual-boot). HDR/144Hz works as expected (the TV is able to output 144Hz on Windows, but only 120Hz on Linux for whatever reason).
  • Update Kernal from 6.17.0-8.8 to current
  • Using Timeshift to revert to a snapshot of my system from a week ago and from a month ago. Issue is exactly the same.
  • Testing other HDMI inputs. HDR will temporarily work, but refresh rate will be incorrect. When I enable “game optimizer” on the TV, HDR stops working and refresh rate is still wrong.

It’s possible there was some update that I installed before powering my system down for a couple days, but I have no idea what that would be or how to find out.

2

Hi @ttgamer, thanks for doing some testing and diagnosis, that helps.

I am no expert on this, but as you’ve tested the OS and PC, is there any chance your TV/Monitor has had a firmware update that has changed its performance?

Apart for that, I’m not smart enough to help on this topic, but I wish you the best with finding an answer.

3

I thought about that too, but I don’t have the TV connected to the internet.

Another troubleshooting step I tried was switching to KDE plasma. This immediately fixed the issue, so I’m forced to blame Gnome somehow. I’m not aware of any updates to Gnome, but I can’t see what else could be the culprit.

4

OK….

I don’t want to go down the wrong rabbit hole here - BUT (and I hate to be pedantic, but it appears I will) - LG TV firmware updates, like many TVs, are delivered OTA (Over-The-Air [sometimes called On-The-Air]). LG FOTA - Support & Help - SO - your TV might have updated without your knowledge.

BUT - I appreciate that having this knowledge does not resolve your problem.