Here’s a steal, the latest Humble Bundle is a must play Metroidvania collection including 7 games that all run excellent on the Steam Deck. You get everything for the price of $15. You can buy it here.
Metroidvania Humble Bundle Games List & DLC List
Hollow Knight (Verified)
Rain World (Playable)
Blasphemous (Verified)
Bloodstained: Ritual of the Night (Playable)
Lost Ruins (Verified)
Lone Fungus (Verified)
Haiku, the Robot (Verfied)