Regardless of what you plug it into, there has to be a way to play music from your home server.

DLNA is pretty much the only open standard in existence to play music stored on one device on a second device, controlled by a third device.

Mount your music using NFS from first device to second device then use third device to control second device? What am I missing here?

Note: they actually included DLNA in their build, so this is moot.

DLNA is few notches below NFS in complexity. It has autodiscovery in the local network and optimized for library organization, control and streaming.

Using NFS instead of DLNA is much like what Russians call "sunset by hand".

Autodiscovery and NFS work fine together. My Kodi box found my NFS exports. I added them. I control Kodi using my phone.

Yes that's how dlna works.

Dlna can be used in different places here. You could also drive it as a Bluetooth sink from another Dlna server. Or use it as a spotify mode. It's not obvious.