Have you heard of "Navidrome"? you can be your own Spotify. It also supports transcoding. For instance, if you are on a phone connected to data, you can set the bitrate to 128kpbs to save some data.
You had your Plex open to the public with that setup. That's not secure at all, unless you wanted anyone to access it.
If you can port forward from your own IP and it's kind of stable, you can run a wire guard server to access your network and Plex.
If you can't portforward you can try a mesh network like tailscale.. there are other solutions as well. The fastest apparently is netwmaker, but you need to have a server with public IP. You can use a cheap VPS.
If a band is popular, albums get ripped/downloaded from streaming services and put on private music trackers within hours of release.
If you don't have space, like recommendations from streaming services, or their app, or not wanting to catalog your music (or setup services that do that), then I would recommend a streaming application.
Mam?
edit: getting into MAM is not difficult if you know English. I got in there on my first try. From there I got to so many other private torrents, I got very good comics and ebooks.
Have you heard of "Navidrome"? you can be your own Spotify. It also supports transcoding. For instance, if you are on a phone connected to data, you can set the bitrate to 128kpbs to save some data.