SteamOS 3.5.5 has been released to the Stable channel for Deck with the following changes:

Display

The default color rendering for Steam Deck LCD has been adjusted to emulate the sRGB color gamut, resulting in a slightly warmer and more vibrant color appearance.

• Added Settings -> Adjust Display Colors, to tune the display's Color Vibrancy and Color Temperature. The settings can be tuned with a preview of a test image (above), or with your running game.
  • Native: The native display color appearance (the color rendering for Steam Deck prior to this update).
  • sRGB: Emulate the sRGB primaries, in a smooth manner that does not introduce gradient clipping.
  • Boosted: Emulate a wider-gamut display appearance, resulting in increased apparent vibrance. May result in gradient clipping.
• HDR can now be enabled in Display Settings if supported by the external display.
• Added HDR Analysis to Advanced Display settings.
• VRR can now be enabled in Display Settings if supported by the USB-C adapter.
• Reworked Quick-Access scaling settings to separate scaling from filtering. Added Stretch and Zoom scaling as new options to handle different aspect ratios.
• Fixed a long-standing issue where the internal display backlight would always stay on.
• Fixed touchscreen orientation while external display is connected.
• Compositing is now avoided in additional scenarios, reducing latency and stutter in situation with multiple overlays on screen.
• Improved latency in certain situations where the application renders slower than the display's refresh rate.

General

• Added support for Steam Deck OLED.
• Fixed an issue where certain workloads would exhibit severe CPU performance issues unless SMT was manually disabled.
• External storage devices are now auto-mounted when connected to Steam Deck. To format or manage storage devices use the new device management interface in Settings->Storage.
• Updated graphics drivers, with many performance and functionality improvements. Improved performance for Starfield. Fixed viewmodel corruption in Amnesia: The Bunker and launch failures for Immortals of Aveum and Kaiju-A-GoGo.
• Improved Bluetooth connection stability, especially with multiple controllers
• Slightly improved sleep resume speed
• Implemented switching between controller bindings and mouse/keyboard desktop bindings by long-pressing Options in the Linux hid-steam driver, to match Steam's default Desktop configuration.
• Improved fade transitions between applications.
• The contents of the performance overlay can now be customized by creating a ~/.config/MangoHud/presets.conf configuration file.
• Fixed a bug where some games could appear stretched if their window size didn't match their swapchain size (eg. Naruto Shippuden Ultimate Ninja Storm 4)
• Fixed Disgaea PC needing to be tapped on before input works
• Fixed physical dimensions reported to games, fixing some issues with an incorrect aspect ratio sometimes being detected (eg. Returnal)
• Worked around a problem where Allow Tearing could cause heavy stuttering if the Performance Overlay or other overlays appeared on screen. Tearing is now impossible in such situations, and the Performance Overlay should be disabled for best results.
• Fixed a problem where keyboard input would not be detected in Overwatch 2
• Controller firmware: fixed an issue where some thumbstick touch sensors would lose touch periodically

Firmware 118

• Added voltage offset settings.

Steam Deck Dock Firmware 121

• Added VRR support.
• Improves reliability when changing display modes via on-screen menus
• Fixed issues with 6bpc color modes, improving high resolution/refresh mode support
• Improves detection of HDMI cable hot-plug events

Updated Arch Linux base

• This update pulls in newer performance, security and stability fixes for the underlying packages that are the foundation for SteamOS
• Most notably, this includes recent changes to KDE Plasma, Steam Deck's Desktop Mode. Full notes on these updates can be found on KDE's website here. Here are a few of the highlights:
  • New window tiling system
  • Updated Discover (app store / software manager) with a new homepage and improved search
  • Discover can now perform system updates from the desktop
  • Updated desktop widgets