The only thing Valve has done was release the Steam Client to Linux.
*countless improvements Valve engineers have made to the the Mesa OpenGL and Vulkan drivers as well as to the kernel graphics driver components. Not just to the AMD graphics drivers for benefiting the Steam Deck’s hardware but also to Zink OpenGL-on-Vulkan and then other common infrastructure. But in this area of the Linux graphics driver support, Valve’s contributions and those of their partners have been incredibly beneficial to the Linux desktop ecosystem even outside gaming. *