Compiling a build supporting Google VR Cardboard or Daydream, with Target SDK 26, as per new Google requirements for distributions, produces unusable builds, that run on black screen. (builds compiled in shipping mode)
All the same settings, just putting Targetsdk 25 or 24, in the Android settings field, produces working builds.
Putting targetsdk to 26, and disabling any VR plugin. Produces working builds.
So, there is something specific related to TargetSDK 26 and Google VR enabled, issue in working togheter.