Plexamp has gotten better lately. It can save your progress on audiobooks now. It’s a per library feature, so I have one library of music (that does not save progress) and one for audiobooks (that does save progress). I used to have trouble with some audiobook formats (M4Bs needed to be converted (really just renamed) to mp4s, but that wasn’t necessary for the last few I loaded. Plex still has a little trouble with standards around multiple authors and different productions (and different readers) of a single book, but that’s more of an ID3 tag problem and is resolved if you’re consistent in normalizing the tags on your library. I’ve also used the syncing features a bunch for offline time (like on a plane or on long trips). For a large library, I see syncing offline files as a necessary feature.

And before the Jellyfin fanboys chime in, if Jellyfin could match these audio and syncing features (and be easier to setup for access outside my LAN and sharing with family), I jump ship in a heartbeat.

“pretty easy” is a bit of a stretch