Plex for audiobooks. It's amazing. There are android and iOS apps too. It will keep your progress across multiple devices just like audible.
It’s a great audio library system, I use PodGrab to subscribe to podcasts and download them and AudioBookshelf for playback and organization etc..
Hey I do this exact thing as well. Would highly recommend if you like self hosting podcasts to listen to.
I use to do the exact same thing until recently when i found that Audiobookshelf can auto download podcast like podgrab does but in a smarter way. And in my opinion the default naming convention on audiobookshelf is better too. Ditched podgrab and haven't looked back.