I agree, Warchild. remapping controllers in steam (historically) has been wonky and I have avoided for much of my life by just using KB+M, lol.... I will say however, so far, with most games I have played on my steam deck, it has done a GREAT job of setting the controller at the start of the game, and so far, I've not had to adjust very much. So I would say Steam really upped itrs game with controller support for the Deck. I mean, they almost had to. It's like the one thing the Deck HAS to do right.

For others looking into this game for these reasons:
I have found Valheim to work just right on Steam Deck, with no wonky controller issues at all.