It’s only currently planned for PC, with no controller or console plans yet — and Mountaintop won’t necessarily allow Steam Deck to join. “Steam Deck is a concern as a cheating vector, and I think our anti-cheat systems may block it right now,” Mountaintop CEO and cofounder Nate Mitchell tells me.
they didn’t say using Steam Deck per se is cheating, but that it’s a cheating vector, i.e. it’s (according to them) easier to use cheats on it than on Windows PCs.