Hey sorry for taking so long to respond.
I haven't gotten very far in the game, just the tutorial and a bit of swimming in the first level. From what I've seen though, both the Linux and Windows builds of the game run pretty well on the Deck after a few tweaks. The Linux build has to be set to use the Steam Runtime otherwise it won't fully quit when exiting the game. The Windows build runs just fine with Proton 8.0 and seems to run a little better than the Linux version actually. I also noticed that the Windows version has startup videos while the Linux version doesn't.
As far as the controls, I've mashed every button on the Deck for both builds and this is what I've observed:
| Left stick | movement |
| Left stick click | nothing |
| Right stick | camera movement |
| Right stick click | first-person view |
| A button | jump |
| B button | nothing |
| X button | nothing |
| Y button | nothing |
| Y button (attack mode) | normal attack |
| Left bumper | nothing |
| Left trigger | crouch |
| Right bumper | toggle attack mode |
| Right trigger | sprint |
| Dpad up | toggle mask |
| Dpad down | elemental attack |
| Dpad left | nothing |
| Dpad right | nothing |
| Menu button | Pause menu |
| View button | Quest menu |
I know development on this version of the game is basically frozen, but if you want to know more about how it works on the Deck I'd be happy to help.