Xamarin iOS app displaying white blank screen on iPad after update to Xcode 11

I had exactly the same problem as you, and even though it could be you already got a solution i will share how i got it working at the end... for those who could still have that same problem.

Note: in my case the issue appeared only on Apps built with XCode 11 that use MasterDetailPage on Xamarin.Forms version < 4.0 and running on iPad: the easiest solution to this issue is simply updating Xamarin.Forms to the latest version (or simply downgrading XCode to a previous version!), but if you (as i was) are not able to update Xamarin.Forms, then keep reading.

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As mentioned in this thread from the Xamarin Forums all you have to do is copy the latest MasterDetailPage renderer from the Xamarin.Forms source and do a few changes.

Since the final script is too long to be added here as text (it exceeds the maximal number of allowed lines), and since i could not find a way to upload a text file, i would point to the thread in Xamarin Forums where i added that script with all the changes needed:

TabletMasterDetailRenderer

Note: Do not forget to change {YourNamespace} for your correct namespace!

This is fixed in at least Xamarin Forms 3.6.0.709228.