Valve will reportedly support Asus ROG Ally and other rival handhelds with its SteamOS. The company, which sells its own gaming handheld, the Steam Deck, has said that it will allow third-party devices to run its Linux-based operating system.Valve will reportedly support Asus ROG Ally and other rival handhelds with its SteamOS. The company, which sells its own gaming handheld, the Steam Deck, has said that it will allow third-party devices to run its Linux-based operating system.