Please follow this document for detail clarify how to build the standalone app and submit to Appstore and Google Play: https://docs.expo.io/versions/latest/guides/building-standalone-apps.html

Open the App.json and add config for package id:

Example:

"ios": {
  "supportsTablet": true,
  "bundleIdentifier": "com.inspireui.listapp"
},
"android": {
  "package": "com.inspireui.listapp"
}

Our demo app results:

ios: https://itunes.apple.com/us/app/listapp-listing-directory/id1355477469

android: https://play.google.com/store/apps/details?id=com.inspireui.listapp&hl=en