The Schedule 1 Steam Deck rating can be seen as a little misleading, at least compared to how Valve has dealt with other games with little to no controller support. You'll need to make some changes if you want to play using the Steam Deck controls; otherwise, a mouse and keyboard are required.
While there's no issue with Valve rating Steam Deck games that don't have the best controller support as playable, it should be called out more explicitly. It's easy enough for someone to just buy the best Steam Deck Dock from our buying guide and hook up a mouse and keyboard to get the full experience, but that defeats the object for players who want to use the Deck as a handheld. Outside of this issue, the Schedule 1 system requirements are super low, which makes running the game on the best gaming handheld a breeze.