Thanks for your feedback, I’m going to make a video for the documentation today explaining step by step how to build to iPhone with Xcode. I’ll send you a link when it’s up.
Regarding your issue, would it be possible to send a screenshot of the purple screen when you open your app (or better, a screen recording)? Are there any error messages in the Unity or Xcode debug log? This info would be helpful to resolve your issue. Also, which version of Xcode are you on?
I’ve done some digging around and have reproduced the problem and found a fix. We are looking in to what is causing it. Changing the following in the player settings of project settings (see picture below) should resolve it:
In the iOS tab, change the colour space to linear.
Not sure if it helps, but with Unity 2019.1.10f on Xcode 11 compiles fine. The only issue that you can see in the Xcode logo is that you need to add in the plist is access to BT that Unity doesn’t have in the settings. Maybe it can help. Not sure.