Highly recommended for anyone with a Steam Deck, or who might game on a Linux machine. On several occasions, Steam has told me that a game is straight up unsupported on Deck, but looking at Protondb, people say it works fine... And what do you know.
Also, some games might only work with ProtonGE, and Steam won't tell you about that.
There are multiple things taken in account for the steam deck compatibility.
One of the issues, can be the very small display. In some cases the game may display small text or require a mouse for some menus, and it will be partially compatible, but in other cases it may be unplayable, or only playable with a mouse.