MoCA is a way to send wired Ethernet up to (300mb/s, at least the version i have) over coax. Verizon fios would provide these devices to send internet to set top boxes over existing coax cabling, but you can get a pair of these devices and send Ethernet in on one side, and Ethernet out the other side.
I have noticed however, it adds a bit of latency to the connection, which may be trouble.
Navidrome is another server that works pretty well, implements the subsonic protocol ( so all the apps that can cache and stream to your mobile device work). You can have multiple logins, or just share out playlists and albums individually to non-authenticated users.