One of the reasons for not detaching is:
“All you need is to distribute your app in the iTunes Store or Google Play. Expo can build binaries for you in that case. If you detach, we can’t automatically build for you any more.”
Is there a guide for building an Expo app for the iTunes store? Will the app appear to be a standalone app in this case (as in, it has its own Icon and you can directly download it on more than one device)?