Does RetroArch work on iPhone Duo?

Not yet. RetroArch runs letterboxed on the inner display, with black borders around an iPhone-sized window. Its latest version is built with the iOS 18.0 SDK, which Apple shows letterboxed on the inner display.

Is RetroArch letterboxed on iPhone Duo?

Apps built with the iOS 26 SDK or earlier show black borders around an iPhone-sized window on the inner display; iOS 27 apps resize to fill most of it, and iOS 27.1 apps fill it completely. Current status: Letterboxed.