I'm using podcastaddict app and in a search I sometimes find free audiobooks. That said.

Librivox.org is multilingual community based for books in public domain

Audible Amazon subscription is interesting where you get buy one get one free with credits byou get each month.

Spotify is crap

And there's a torrent page focused on books, audiobooks, music, radio 📻

But you need an invite which bI don't have. I'm planning to get one in the next IRC session