This still does not work. Any update? Anyone gotten it to work? Even tried on the June 2018 release of 4.19 with AR Core 1.3 build directly from Google and it fails, same error.
SOLUTION!!! (EDIT)
I got it to work. So I tried to create the database manually using arcoreimg in cmd with the correct commands, and it throws an error that there isn’t enough feature points to track accurately.
Make your tracker image more complex, bam it worked 100%!
EDIT 2: I noticed the 4.20P5 build is missing the Tools section of the ARCore, so I tried to copy/paste them from 4.19-ARCore and it failed still.
So this does not work in 4.20P5, you must use the 4.19-ARCore source build from Google.
GitHub: