I know this will not apply to a lot of people but this was a mixed bag on the Steam Deck. At least it is native Linux so I don't gotta deal with Proton.
First off, the game only seems to support 16:9 aspect ratios judging by the available resolutions I had. Not a big deal but since the Deck is 16:10, there is some small black bars at the top and bottom. Slightly annoying but certainly not the first game I've dealt with it.
I know the game lacks controller support, I saw that in the supported inputs. I figured I can just look at the controls in the settings and just use a custom Steam Input layout. Unless I missed something obvious, I couldn't find a layout. Which made it much harder to set something up.
The game auto set the resolution to 960 x 540. Not an issue, I just set it to 1280 x 720... and now the text is tiny and barely on the text box. This seemed to resolve itself by switching the resolution back and forth a few times though.
The game itself runs just fine though. In the hour I played there was no significant bugs and I got the general impression it was pretty polished and a lot of care went into this. I 'm not here to bash the game, just some observations I made while playing on my Deck.
I wish you nothing but the best devs and hope the launch goes well! Have a good one :)