Valve has released a preview update for Steam Deck OS 3.5. With this update, the handheld console gains support for HDR and VRR on connected external monitors, which support the imaging techniques.
In the release notes Valve states that HDR and VRR can be enabled in the settings menu. As for VRR, the end user must have a USB-C cable that also supports the technology. Valve has slightly adjusted the way colors are rendered. This will make colors appear slightly warmer and more saturated. The color temperature and saturation can also be changed via the settings menu.
Steam Deck OS 3.5 also brings an update to the graphics drivers. This should make Starfield run better on the device. Minor bugs are being fixed and various improvements are being made.
Steam Deck OS 3.5 Preview Update