There have been a few mentions of Navidrome. I find it works well for sharing at an album or even artist level. It can do playlists as well. But you must explicitly choose what to share, at which point it’s generates a unique URL and will generate a web player and zip if you enable the option to download.

You can, of course, just make user accounts and distribute credentials.

If you’re needing to offer browsable folders to easily copy, basically a filesystem-like experience, it’s probably not the best tool.

Edit: one more thing to point out is that navidrome, jellyfin, and airsonic all construct music libraries differently. Navidrome is using tags, jellyfin uses file names, airsonic uses directory structure. Not sure about Plex.