Navidrome + Substreamer, but I'm starting to use the Navdrome webapp as my main player - it links into the car's volume and next/previous, and works very well. On your desktop you can install it as a webapp with an icon on the desktop and a separate window.

I also have metube which drops songs directly into my downloads folder.

A regular shell script to create playlists from each folder, so I can arrange songs onto folders and get playlists.

Can share a playlist or song anonymously, or add a user to the system

Amazingly simple, powerful and complete.

Anything for iOS?

Never heard of symfonium, I'll need to google it.

Best setting ever!