Works great
I had no issues with this game and I was able to play through everything no problem.
Loved it on the Steam Deck
Worked great out of the box. When the game starts, you'll have to use a couple educated guesses to figure out what button gives the game input for the keyboard key they show on screen, but it's pretty natural and didn't take me more than a few seconds to figure out. Lovely little experience on the Steam Deck, it felt great to play Teacup on a handheld.
Finished game with no issues
Game plays fine but it shows keyboard buttons instead of xbox ones.
It didn't show controller layout only keyboard but was fine playing with the controller.
I played it in Desktop mode on an external monitor so I'm not sure how it would fare in handheld gaming mode, but considering that the game is also on Switch I can't imagine any issue regarding it while mobile. As for my experience I had no issues whatsoever.