Steam deck could conceivably use a signed bootloader to provide some of the guarantees that an Anti-cheat is looking for. But regardless, Valve sounds committed

Steam deck could conceivably use a signed bootloader to provide some of the guarantees that an Anti-cheat is looking for. But regardless, Valve sounds committed to describing the steam deck as "still a PC [that you could put windows on]". For non-steamdeck Linux users, at least running on Linux shouldn't be a disqualifier for the Anti-cheat software.