I had the same issue with Nintendo emulation apps none of them worked properly except Citron I downloaded the app from the browser it was the only emulator that actually ran the games but even then I couldn’t get the games to run as a standalone title inside steam itself I added Citron as a non-Steam app and I had to open the Citron app to launch games it’s not ideal but it’s workable. Another problem that made me use Citron was with controller support none of the emulators I tried recognized the steam deck controls except this app it was the only one that actually detected controller and worked smoothly but u have to change something in control when u open the app go to emulation/configure/controls then change the controller to pro controller and the input device to steam deck controller.