Building Expo apps on your own hardware is definitely supported. Specifically, run "npx expo prebuild:{android,ios}" to generate your project's "android" and "ios" directories. Open them up in Android Studio and Xcode (or use their command-line equivalents), respectively, and build.

The managed services (EAS) are optional for Expo apps. The independence between Expo, the free and open source framework, and EAS, the hosted service offering, is something the Expo team consciously works on.