Navidrome is my favorite, by far. It's like a personal Spotify. It also has built-in subsonic support.

Syncthing is another I could not live without. All devices upload to my server and my server gets backed up to S3/backblaze type service.

Plex for movies. But I may look at Jellyfin soon.

I use Calibre-web, but it's really not my favorite. Okular is so much better. And Calibre is a chore to use and overkill for my needs. Books organized into folders is about as far as I care to organize. Thumbnails are nice though.