Big news! I finally got my hands on a Steam Deck and now the game is playing really well on the deck. The two main visual bug fixes are:
The cursor now properly displays in the center of the screen
The UI and menu items are scaled properly
The tradeoff right now is that we have some small black bars to contend with due to the aspect ratio different, but otherwise, it should be good!
Cursor now shown in center of screen:
UI and menu items show correctly: