As we suggested it would be, Valve has announced that experimental Vulkan support for Counter-Strike: Global Offensive (CSGO) has landed and can be tried out right now. This is available only for Linux too.
Coming in a small update on December 14, the only other change was a fix for "input delay after closing radial menu".
You don't need to opt into any Beta, as it's in the main game client. All you need to do is add
-vulkan as a Steam launch option for the game. Do so by right click -> properties and then enter it in the text box.
This is of course preparation for the Steam Deck, to hopefully bring the performance up to a level that makes it as smooth as possible. The same was done before with Portal 2, Left 4 Dead 2 and Half-Life 2.
You will probably find it stutters a fair bit initially, like Valve's other games that added in DXVK-Native and Windows games played with Steam Play Proton it needs to build up a shader cache. Over time, Valve will usually gather it all up and offer it all as a download like they do for other games, to have it processed before starting. In my own testing, the stuttering was really bad. Still, it's experimental and hopefully more optimizations to come.