This is becoming a serious issue. Dear expo, can you please update us? It is stopping us from going live.
I even get e-mails form Apple about it:
Dear Developer,
We identified one or more issues with a recent delivery for your app, … Your delivery was successful, but you may wish to correct the following issues in your next delivery:
SDK Version Issue - This app was built with the iOS 12.0 SDK. Starting March 2019, all iOS apps submitted to the App Store must be built with the iOS 12.1 SDK or later, included in Xcode 10.1 or later.
After you’ve corrected the issues, you can use Xcode or Application Loader to upload a new binary to iTunes Connect.
Best regards,
The App Store Team