The iOS .ipa and the android .apk are bundled with each Github release.
Screenshots
Building for android
1. Run `flutter build apk --split-per-abi`
2. Grab the apk release build file with your required ABI
Building for iOS
1. Run `flutter build ios --no-codesign`
2. Copy `./build/ios/iphoneos/Runner.app` into a `Payload` directory
3. Compress `Payload` and change extension to `.ipa`