I'll second navidrome.
I've also added bonob to expose it to some sonos hardware I got for free. I've found it's the easiest way to get custom music and streaming radio into sonos. Music Assistant buffers for some reason.
I'm having the same issues with exposing it. I have mine behind Caddy+caddy-security and it works well through the browser, but I haven't found a native app that can handle that method. I think I'll add it to tailscale eventually to work around that.
Here are some features off the top of my head that some backups software might have that other don't, or that you'll want to consider when choosing or making a system:
I'm not sure which of these exist in free software, my experience is mostly on enterprise software. A backups system can be as simple as a rsync/zip cron job or a full integrated system depending on what you need.