Prologue for iOS is a Plex audiobook player that is better than any audiobook player has a right to be.
Here's a good guide on how to set up Plex for proper metadata with audiobooks: https://github.com/seanap/Plex-Audiobook-Guide
Here's a good guide on how to set up Plex for proper metadata with audiobooks: https://github.com/seanap/Plex-Audiobook-Guide
I use Android, iPadOS, Fedora Linux, MacOS and possibly in the future Windows (my last job required it, my next job might too) and unless the standard plex app supports audiobooks I doubt I'll find much consistency using native apps for each of those operating systems, if they even exist on all of them
I've heard good things about audiobookshelf [1] as a cross-platform alternative, but it is pretty early in development.