I thought I would put in a plug for the Libro.fm audiobook program. I switched from Audible in March to it and think it is a good alternative to Audible. It helps your local bookstore and all the files are DRM free and MP3.
I don't like to listen on my phone so I like that I can download these onto an MP3 player easily. They do have an app that looks like it would be similar to other audiobooks services.
Take a look, it might be worth it to check out.
https://libro.fm/
One reason I left Audible is their change to enhanced files, I know they want everyone to use their phones to listen and they say the change improved the sound quality but it makes the file twice as big as before and therefore harder to use an MP3 player.