Hey @jknouse,
thanks for your review.
I removed that from the readme now.
However, Oxygen Builder is supported by Passster.
I even wrote an entire tutorial about that right here: https://patrickposner.dev/tutorials/password-protect-sites-with-oxygen-builder/
But, I must admit that you need at least some experience with Oxygen Builder to make that work (like adding a header and footer to your theme).
Thanks again,
Patrick