Remember all the ruckus with various US states introducing operating-system level age verification laws? Colorado and California thankfully exempt open source.
HID Remapper is a useful open-source programmable adapter for USB input devices, with a recent release adding support for Valve's new Steam Controller.
The official Vulkan API Conformant Products list from The Khronos Group recently had Valve's Steam Machine appear on it - so a release is likely quite soon.
Bringing together the worlds of twin-stick arcade shooters with crafting and exploration, Veridian Expanse is another indie game with a demo worth a go.
Valve released the latest small stable update to their Linux distro with SteamOS 3.7.25, along with SteamOS 3.8.5 Beta bringing extra fixes and enhancements.
D7VK continues bringing enhancements for running retro Direct3D Windows games to run nicely on Linux / SteamOS, with a fresh release boosting 2D games.