Audiobookshelf works great and is very easy to setup using Docker. I get most of my audiobooks through Downpour. They have a subscription that gives credits to redeem for audiobooks similar to Audible, but they are drm-free. I download the audiobooks and move them to my NAS that has Audiobookshelf running on it. Audiobookshelf has a web client and apps for Android and iOS (TestFlight beta).
They are not ready for regular use yet. Performance is poor and battery life is bad. It’s fun to play with my Pinephone and watch the software slowly improve, but there is no way I could use it as my primary phone.