Public bug reported:

Summary
Green flickering and horizontal stripes appear across multiple applications on 
Ubuntu 26.04.1 LTS with a Radeon RX 9060 XT and a Xiaomi 27-inch monitor 
connected via DisplayPort at 2560x1440 180 Hz. Switching the Ubuntu desktop 
appearance/theme triggers the same artifacts. After switching only the refresh 
rate to approximately 120 Hz, the display appears normal. This is a short 
observation, not yet a long-duration stability test.

Steps to reproduce
1. Start the Ubuntu GNOME Wayland session.
2. Set the DisplayPort monitor to 2560x1440 at 180 Hz, fixed refresh (VRR is 
not selected).
3. Open applications such as Chrome, Discord, LimCore, or the ChatGPT desktop 
application.
4. Switch the Ubuntu desktop theme/appearance and observe the display.

Actual result
Green flickering and horizontal stripe artifacts in multiple applications.

Expected result
No image corruption when using the monitor's advertised 180 Hz mode or 
switching desktop appearance.

Workaround tested
Use 2560x1440 at 119.9976 Hz instead of 179.9996 Hz. Artifacts appear to stop. 
Resolution, scale (100%), and VRR selection were not changed. Intermediate 
refresh rates have not been tested.

Environment
Ubuntu 26.04.1 LTS (resolute)
Kernel: 7.0.0-38-generic, package 7.0.0-38.38
/proc/version_signature: Ubuntu 7.0.0-38.38-generic 7.0.14
GPU: Sapphire AMD Radeon RX 9060 XT, 16 GB (Navi 44 / gfx1200)
PCI ID: 1002:7590, subsystem 1da2:a493, revision c0
Kernel driver: amdgpu
Mesa: 26.0.8-1ubuntu0.3
GNOME Shell: 50.1-0ubuntu1.4
Mutter common: 50.1-0ubuntu2.5
linux-firmware: 20260319.git217ca6e4.1ubuntu
Session: Ubuntu GNOME on Wayland
Monitor: Xiaomi Corporation 27-inch / Mi Monitor
Connection: DP-1, DisplayPort
Resolution: 2560x1440, scale 1.0
Affected mode: 179.9996 Hz, fixed refresh
Workaround mode: 119.9976 Hz, fixed refresh

Additional investigation
- Rounded Window Corners Reborn version 25 initially generated errors. 
Disabling it appeared to help briefly, but artifacts returned when switching 
the desktop theme.
- The issue persisted after logging out and back in with this extension 
disabled, so it does not depend solely on stale extension state.
- Other enabled extensions: Ubuntu Dock, Desktop Icons NG, Tiling Assistant. A 
session with all extensions disabled has not been tested.
- Discord uses native Wayland; the ChatGPT desktop application uses 
X11/XWayland. Both were affected.
- GPU temperatures sampled during investigation were approximately 32-35 
degrees Celsius; no load or VRAM stress test was run.
- No GPU reset, ring timeout, or GPU VM fault was found in the inspected 
current/previous boot logs.
- Repeated kernel warnings were observed: workqueue: dm_handle_vmin_vmax_update 
[amdgpu] hogged CPU for >10000us ... consider switching to WQ_UNBOUND. Their 
relationship to the visible corruption is unconfirmed.
- No alternate DisplayPort cable, GPU port, or monitor has been tested. 
Driver/compositor and physical display-link causes have not yet been 
distinguished.
- No screenshot or video of the corruption is available yet.

Suggested initial component: linux (amdgpu display); please reassign if
investigation points to Mutter or Mesa.

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/2172197

Title:
  [amdgpu] RX 9060 XT: green flickering and horizontal artifacts at
  1440p 180 Hz, absent so far at 120 Hz

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