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).