The issue comes down to how the device interacts with your computer. Just like the original version, the new Steam Controller has no native Windows drivers. This means the hardware relies entirely on the Steam app to function properly. If you do not have the game running via Valve’s storefront app, your shiny new gamepad turns into a useless piece of plastic.
Gamers Nexus also reported this and there are a lot of other news outlets also covering this. It is kinda the same as with the steam deck where I noticed that the inputs just don’t work until steam is launched. I really don’t like that I have to have Steam running for this controller to work. I don’t know if it is a dealbreaker for me, yet, but it really put a damper on my enthusiasm about it
a lot of the features of the controller are not supported by X input, I still think they should’ve added an X input switch somewhere somehow, ideally this device gets its own custom driver for windows, since it is fairly unique generic controller drivers just wouldnt provide full fearure set, hopefully valve makes a full open source in trww driver for it on linux which can be used as a basis for other devices like this,
hopefully valve also provides documentation on how provided ingame integration (basically the game turns on its own “steam” input) and a proper sdk, that would allow developrs to integrate natively the controller without needing steam