Even the game’s page on steam is usually useful. If you click on details in the deck verified page it tells you exactly why it’s not verified. Most of the time it’s something like not selecting the deck’s screen resolution by default, or needing the keyboard to enter a character’s name.
A great deal of non-deck verified games also work out of the box. ProtonDB has good information about how well something will run on Linux.
Even the game’s page on steam is usually useful. If you click on details in the deck verified page it tells you exactly why it’s not verified. Most of the time it’s something like not selecting the deck’s screen resolution by default, or needing the keyboard to enter a character’s name.
It’s tried, I have a lot installed. But it’s just so easy with the verified ones when it all just works with minimal mucking around