I selfhost kavita for about 30 ebooks and use KavitaEmail to send epubs to my kindle. I also tried out audiobookshelf only for podcasts and wasn’t quite up to my current workflow that antennapod running only on my phone exceeds at. I also recently saw audiobookshelf can host epubs and send them via SMTP via one container so once the android app for the latter comes out of beta and has better local file and androidauto support I may give that a shot again.