I ended up spinning up audiobookshelf. It’s fine for audiobooks, and I immediately installed Lissen (alongside ABS) and it is clearly preferable to me.

Lissen does not recognize ebooks at all, and I also didn’t have success with the comic book I tested on the ABS client, so I may try another service for those. For now audiobooks are the higher priority and I am very happy with those. Thanks for the input - I really appreciate it.