@jimmylee - sure, makes sense, but the problem is I need a bit of native code to actually get the IDFA (and respective advertising identifier on Android). AdSupportIOS in react-native was meant to do this for iOS but it’s not linked by default (and therefore not linked for Expo), and moreover, it’s been deprecated as of the latest react-native (0.48).
Sounds like for my immediate use case ejecting might be the only option, unless something like react-native-idfa can be added before SDK 21 was released, or something!