If it is helpful to other people here is how I manage my ebook library with flatfiles and heterogeneous devices (Android, macOS, iOS, Kindle, etc)
I have my own eBook library hosted with copyparty. It is a single binary. Runs on plain files. And speaks OPDS for integration with KOreader (Kindle) or Readest (iOS/macOS). https://github.com/9001/copyparty#opds-feeds
It also speaks webdav so I can quickly sync everything via rclone to an SD card on devices like an Android tablet.
I really like the convenience of flat files and multiple protocols.
I absolutely love audiobookshelf for audiobooks. And I currently use it for my epubs, but it does not handle that particularly well. It doesn't save progress consistently and the UI for page flipping leaves a lot to be desired. Definitely going to check out how OP's library works
I haven't spent much time with calibre-web in a long time but can confidently say BookOrbit blows it out of the water in terms of functionality. I love that I can have one app that handles books and audiobooks. The ecosystem of apps that work with it is growing quick too, Apogee for iOS being a standout for me. They recently added readaloud support (like Amazon Whispersync or Storyteller) natively in the app, which I've never seen done before.
I have no relation to BookOrbit except I'm a very happy user.
I have my own eBook library hosted with copyparty. It is a single binary. Runs on plain files. And speaks OPDS for integration with KOreader (Kindle) or Readest (iOS/macOS). https://github.com/9001/copyparty#opds-feeds
It also speaks webdav so I can quickly sync everything via rclone to an SD card on devices like an Android tablet.
I really like the convenience of flat files and multiple protocols.
I have no relation to BookOrbit except I'm a very happy user.
(I have my Calibre library in iCloud Drive, but if I wasn't inside the Apple Ecosystem I'd use R2)
https://garagehq.deuxfleurs.fr/