This update is only for the Steam OS Preview channel and brings a Raytracing fix for Persona 3 Reload, better OLED trackpad control and HDR stability.
The full release notes are as follows:
Improved performance of ray-traced reflections in Persona 3 Reload
Slightly improved corner tracking on Steam Deck OLED trackpads
Fixed a possible session crash when connecting an HDR display
Fixed a rare session crash on application exit
You can follow live updates here