If you haven’t done this yet, I highly recommend you install Libation and liberate your audiobooks from Audible.
It’s been a month since I first learned of this fantastic, free, libre, open-source project from u/darchangel(not sure if they’re on the fediverse). And unlike so many other OSS projects this one is dead simple to use, accessible to the less technical, and very well documented.
I was able to download my entire Audible audiobook library, with included documents, in just minutes.