Exporting to Kindle Fire 7 (Android 5.1). HelloARVideo test app runs fine, except that on discovering the targets the 3D geometry appears but with a black surface and no video.
This with Easy AR 2.3.0 and the latest 2018 unity.
When I downgraded to the the most recent 2017 unity, the same Easy AR package worked fine.
My issue is therefore currently resolved, but I wanted to make others aware of the problem and of my solution.
Thank you for a wonderful product.