nyepepper

this already exists in jellyfin

My requirements towards one solution is almost the same as yours. I've tried for a (relative) long time with jellyfin since I don't like the half-assed selfhosted/commercial approach from plex. I think jellyfin works great for:

* multi-user with setting limits and access * multiple devices * chromecasting everything * native apps (the one for firetv works perfect) * meta data scrapping * automatic subtitle downloading and managing * creating playlists and collections

I tried using jellyfin also for: * music * audiobooks * ebooks but without any satisfactory success. I now use calibre-online for ebooks and am yet to find something good for audiobooks/music.

I don't think you will ever find a PERFECT selfhosted completely opensource tool for everything and by now i think that's fine.