iOS + Android apps will crash on launch if Event Driven Loader is disabled.
Confirmed in 4.23 MAIN at CL 5035898
1. Create new project and configure for iOS
2. Set Project Settings -> Event Driven Loader Enabled to False
3. Deploy to iOS Device
Result: App crashes on launch
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-70402 in the post.