SteamOS VRR Flickering on ROG Xbox Ally X

VRR brightness flickering on ROG Xbox Ally X internal display when screen is idle (SteamOS 3.8.14)

Hardware

Device:
ROG Xbox Ally X

Internal Display

BIOS:
RC73XA.317

Software

SteamOS Version:
3.8.14 (20260703.1)

Kernel:
6.16.12-valve24.4-1-neptune-616-gfe145653a794

Game Mode:
Affected

Desktop Mode (KDE):
Affected

Issue

When Variable Refresh Rate (VRR) is enabled on the internal display, the entire screen repeatedly changes brightness (bright → dim → bright → dim).

The effect resembles high-frequency global brightness flickering.

This occurs:

in SteamOS Game Mode
in Desktop Mode (KDE)
inside games
Reproduction
Boot SteamOS.
Enable VRR.
Stay on the SteamOS Home screen.
Stop all user input.
After a short period, the display begins global brightness flickering.

The issue is 100% reproducible.

Interesting observation

The flickering immediately disappears whenever the UI continuously updates.

Examples:

Hovering over a button that plays a looping highlight animation.
Continuously moving the cursor.
Any UI animation that continuously renders.

As soon as the screen becomes mostly static again, the flickering returns.

Another observation

Using Decky Framegen ("Duck"/Frame Generation plugin) also prevents the flickering completely while it is active.

This suggests the issue may be related to the display pipeline entering an idle presentation state rather than VRR itself.

Comparison

The exact same hardware does NOT exhibit this issue under:

Bazzite
ChimeraOS

Only official SteamOS shows this behavior.

Expected behavior

VRR should remain stable without global brightness flickering while the UI is idle.

Additional notes

Performance overlay does not show FPS or refresh-rate changes during the flickering.

The issue appears independent of Game Mode/Desktop Mode and only occurs on official SteamOS.

Start by reproducing the issue on the ROG Xbox Ally X with SteamOS 3.8.14 and VRR enabled, comparing an idle screen with continuously updating UI in Game Mode and KDE Desktop Mode. Investigate the display pipeline behavior during idle presentation and compare with Bazzite or ChimeraOS; done when the cause is identified and VRR remains stable without brightness flicker.