Waydroid installer for SteamOS, lets you run Android apps on Deck

Android games are normally going to be inferior to Steam games, but this is still a nice option for games that aren't available on Steam or can't be played due to anti-cheat reasons.

You can read more about Waydroid here. There are reasons to believe valve is working on adding official Waydroid support to Deck, but until then you can install it this way.