The Steam Deck might be the most popular Linux PC ever, though you’d be forgiven if you haven’t realized that its SteamOS software is technically Linux. The Proton compatibility layer is the Steam Deck’s special sauce, allowing games made for Windows to run on Linux without a massive headache. Now Valve is apparently testing a version for ARM hardware. “Proton-arm64ec-5” is not public, but was spotted in the SteamDB.info database (reported by Tom’s Hardware), with that “arm64” label being indicative of a version of the tool designed specifically for ARM-based devices. ARM hardware is in a lot …