If you already use Nextcloud AIO, you can easily enable the Jellyfin community container, the caddy (reverse proxy) container, and the fail2ban container which should give you a pretty good setup pretty easily.
I always store my mp3, flac and wav files locally on my PC HDD or microsd on my phone. I have set-up navidrome to stream my music and to move away from microsd in the future.
For new music, I will use YouTube or Spotify (free) before downloading them locally. I used to pay for Spotify premium, but I stopped not because of privacy reasons, but because I want ownership of something that I’ve paid for.