Alright, it is mostly fixed on my end. Disabling Mobile VR Multiview was the solution.
Make sure you are packaging and deploying your game. When “launching” in the DebugGame config, I actually need to restart the app once it is on the device to get rid of the black screen.
Other notes - I also merged in a018f ( fix broken mobile scene captures ), but this didn’t seem to change anything.
Another bug - Daydream apps now crash if there are any blueprint references to the steam chaperone or oculus guardian. This was not an issue in 4.14.