I gave up today, paid a $50 restock fee and returned the phone. I personally don't care if the FPS reader is capacative, ultrasonic or pixie dust, I expect it to work, at least close to the 90+% that I see on my S8 and the S7 edge before that. No learning curve, lots of people are doing it all wrong, etc. When I saw today's Samsung message saying it would get better in future updates, that's when I knew that I was making the right decision since based on how 'quickly' they update devices, I chose to cut my loss and move on.
I wasn't paid to be a Beta tester, it's a $900 device not a Blu special, so I expect more.