I don’t know about the rescan requirement you have, but Symfonium handles my very large Jellyfin music library (and supports local libraries and many other libraries as well). Has good equalizer options including volume boost and very good native theming that supports dark mode and material you. Paid app but very well worth it if you listen to lots of music on Android. I’ve been using it for years and it’s regularly updated, I’m very happy with it.