In brief: There are a few ways to play PC games on Android devices such as phones, but it often requires streaming them, which isn't always ideal, and may require a subscription. But a free, open-source app brings Valve's Steam client to supported Snapdragon-powered Android devices, running games locally and without changing the OS.
Called DroidDeck, the app runs PC games locally using ARM64 Proton and x86 translation. There's no streaming, and it doesn't ask for root access or to replace Android with a different operating system.
DroidDeck runs Valve's ARM64 Linux Steam client in Big Picture mode, so it should be pretty familiar. Windows games run through Proton, while FEX handles x86 instruction translation.
Steam users can access their libraries directly and download the games onto the device, just like they would on a PC.
The app also boasts GPU driver switching, AMD FSR and Snapdragon GSR upscaling, and frame generation through Lossless Scaling, provided you own a copy on Steam.
DroidDeck won't work on every Android device out there. According to the project's GitHub page, you'll need Android 9 or newer and supported Adreno graphics, officially Adreno 730 or newer, including the 8xx series. Adreno 6xx support is experimental, while Mali, Xclipse, PowerVR and Adreno 710 aren't supported.
You'll also need around 3GB for the Linux runtime, another 1.1GB if you want the optional desktop and emulators, and plenty of space for your games.
Before launching Steam, Android's child-process restrictions must be disabled. You can download the APK from the project's GitHub releases page, then install the runtime and sign in.
As for what performance you can expect, YouTube channel ETA PRIME tested the app on a Redmagic 11 Pro with a Snapdragon 8 Elite Gen 5 and 16GB of RAM. Cyberpunk 2077 ran at an impressive 60fps using medium settings.
DroidDeck isn't the only app that offers this sort of functionality. Winlator runs Windows applications using Wine and Box86/Box64, while GameNative also lets you download and play games from your Steam library locally, with cloud saves and community configurations. DroidDeck's main advantage is getting Valve's actual Steam client and its familiar Big Picture interface.
Don't expect every game in your library to work, though. The developers say compatibility and performance vary by device, so you may need to experiment with the settings before finding the optimal experience.