Facebook Portal is a video calling device. It runs Android, but without the Google Play Store, so RetroArch cannot be installed on it. It can run the web version of RetroArch in the Portal's browser instead. Expect lower performance than on a dedicated gaming device.

Running RetroArch on Facebook Portal

1. Pair a controller: open the Portal's Bluetooth settings, put the controller in pairing mode and select it in the list.
2. Open the web browser and go to web.libretro.com.
3. Choose the core for the system you want to play.
4. Load content. The web version offers homebrew games for each core under Downloads in its main menu.