If you’d like to distribute your Flutter app to iOS-using testers via Firebase Distribution, you’ll need to build IPA files. IPA files are simply iOS Application files that behave like APK or app bundles on Android.
Unlike APK or app bundles however, you can’t just run a flutter build command and create an IPA.
flutter build appbundle
flutter build apk
This article will show you the fastest way to build an IPA for your Flutter app.