Did some more testing. The white screen/delay only happens when the app is provisioned for debugging and started for the first time in the simulator. When i terminate the app and start it on the simulator again (w/o debugging from xcode) all went smooth. No white screen, no delay. So it looks like there is some kind of debugging/first run overhead that causes the delay aka white screen (system launch screen) to be visible for that long time.

Same here. Updated xcode & simulator yesterday and out of sudden ios apps when started show a white screen for seconds before the main application screen (i.e. a splashscreen) appears. Added print() to trace but it looks the delay happens not in user code. Looks like loading libs during the startup process takes ages before user code starts running.