Oculus Unity Integration is broken for Unity 2018.1 on Quest

Unity: 2018.1.9f2
Oculus SDK: 12.0 / 13.0 / 14.0

It looks like the last few versions of the Oculus Unity Integration are not working on Quest when built from Unity 2018.1 anymore.

Reproducing:

1. Create a new Unity project in Unity 2018.1.9f2
2. Download Oculus Unity Integration 1.43 and import it into the project (enough to import just the VR subfolder)
3. Open the Oculus/VR/Scenes/Cubes sample scene and set it as the only scene in the build settings
4. Open the project settings and make sure these settings are correct:
   * Virtual Reality Supported is checked in the 'XR Settings' section
   * Only the 'Oculus' SDK is selected in the 'XR Setting' section 'Virtual Reality SDKs' list
   * 'Minimum API Level' is set to API level 16 in the 'Other Settings' section
5. Build and run the application to Quest

This should run correctly.
Now try following the same steps, but replace the version of the Oculus Unity Integration in step 2 with version 12.0 or above and the application will not run correctly anymore. Instead, it will open up on a flat screen inside the Quest OS.

Notes:

• As a shortcut, instead of following all these steps from scratch, I close Unity, delete the Oculus folder, open unity and re-import the Oculus Integration.
• I tested this on versions 1.42, 1.43, 12.0, 13.0, 14.0
• I can't upgrade my game from 2018.1 because it relies on UNET for multiplayer, and UNET stops working above this version (even though Unity's documentation suggests otherwise).