Using Discover store to download apps is easy on the Steam Deck. You can download Lutris, Stremio, ProtonUp-Qt like apps for your personal use.
1) Find Discover store on your Steam Deck it should be on your navigation bar at he buttom of the screen
2) If you are unable to find Discover Store or unpinned it you can just use the start menu or search inside the start menu
3) After you opened the Discover Store you can use the search bar to install apps or you can just browse the Discover Store
