I saw exactly this problem for someone using one of the other optional Universal Modules and ExpoKit but there was no solution posted.
I have an app that works within expo. I then eject to expo kit and follow these steps for adding face detector https://docs.expo.io/versions/latest/expokit/universal-modules-and-expokit/. When I run pod install I get
Unable to find a specification for UMCore
depended upon by EXFaceDetector
here are my dependencies:
"@expo/samples": "2.1.1",
"expo": "^31.0.2",
"expo-face-detector": "^4.0.0",
"expokit": "31.0.2",
"native-base": "^2.8.1",
"react": "16.5.0",
"react-native": "https://github.com/expo/react-native/archive/sdk-31.0.0.tar.gz",
"react-native-progress-bar-animated": "^1.0.6",
"react-navigation": "^2.18.2"
Any help would awesome!