refresh rate control for external displays doesn't do anything

[gaker19sc]

Your system information

• Steam client version: 1733265492
• SteamOS version: 3.6.20
• Opted into Steam client beta?: No
• Opted into SteamOS beta?: No
• Have you checked for updates in Settings > System?: Yes

Please describe your issue in as much detail as possible:

When I plug my XREAL Air into the Steam Deck and enable refresh rate control for external displays in the developer options, the slider doesn't actually do anything, my refresh rate will stay at 60hz. I've tried different resolutions including 1280x800 or 1920x1080, but no luck.

Steps for reproducing this issue:

1. Plug in an external display
2. Enable refresh rate control for external displays in the developer options
3. Change the refresh rate in the Quick Access Menu

Expected result: The refresh rate changes to the value I set or I get a black screen if the display doesn't support the resolution
Actual result: Nothing

[ds22x]

I've been experiencing the same issue after the 3.6 update was pushed to stable.
Very annoying indeed for games I was able to run at a frame rate lower than 60 but higher than 30 for performance reasons on my monitor.