Mobilism, Audiobookbay, yandex (the search engine yes… very easy if you just use key words in your queries). I’m sure private forums are helpful as well.

Edit: I use mobilism quite a bit and audiobook websites that have links for rapidgator or other hosts. Having a debrid service (all, real, etc) is super helpful because I can usually use the premium link service to convert the link so I can download at full speed. Not all hosts are supported but its not often I find a link from a host that isnt supported. If this does happen, I just bite the bullet and go ahead with a slow download.

https://librivox.org/ free public domain audiobooks. Lots of classics in lots of languages.

If all else fails with others’ comments, try your public library. Seriously.

You can access audiobooks for free, from your local library, using the Libby app.