Brightness level does not save on Steam Deck

[Tech-How]

Your system information

• Steam client version (build number or date): 1721173382
• Distribution: Arch (SteamOS 3.5.19 20240422.1)
• Opted into Steam client beta?: No
• Have you checked for system updates?: Yes
• Steam Logs: steam-logs.tar.gz
• GPU: AMD

Please describe your issue in as much detail as possible:

When the brightness slider is altered in game mode, then the system is rebooted, the brightness will revert back to the system default. After moving the brightness slider 1 notch to the right or left in game mode, the value will be set correctly. This indicates that the Steam client remembers the user specified brightness value correctly, but the OS is ignoring it upon boot up.

Steps for reproducing this issue:

1. Set the brightness value to a very high or very low value in game mode, so you can observe the change.
2. Reboot the system
3. The brightness resets to default and does not remember your value pre-reboot.
4. Adjust the brightness slider by moving it 1 notch to the right or left, then back. The brightness is restored.

Additional information:

Steam Deck LCD 256GB Adaptive Brightness disabled The Steam client started at about 15:24, and I dragged the brightness slider at about 15:24.20, if this is helpful information when examining the logs. Feel free to reply if additional information is needed.

[Tech-How]

Just adding a note, if the Steam Deck has crashed, resulting in the "Verifying installation" message upon boot up, the brightness will be restored correctly. The brightness adjusts back to the user preference only if/when that verification screen is displayed. (Or possibly other scenarios I haven't discovered yet)