After some digging around, I think that the librivox pages like https://librivox.org/moby-dick-by-herman-melville
do not provide data about their
RSS feeds in a way that Google will index them as podcasts.
According to https://developers.google.com/search/reference/podcast/homepage-requirements
Google wants to see a link like:
which could be embedded in the <HEAD> section of the page.<link type="application/rss+xml" rel="alternate"
title="Moby Dick, or the Whale by MELVILLE, Herman" href="https://librivox.org/rss/753"/>
Of course, being in the public domain there are many other sources for the librivox readings, but I thought
it would be nice if Librivox got the credit and showed up when naively searching Google.
Thank you for providing a great resource!