I use a Chromecast Audio connected to my music system via an optical sPDIF cable and also a regular Chromecast connected to my TV using HDMI (in a different room).
My music files are sitting on a network share on a Windows 10 PC which works a dedicated "server", always on in my household.
On my Android phone, I have VLC
VLC is able to see files on my server.
Before playing music in VLC, I tell VLC to cast to Chromecast.
When I hit play, Chromecast plays the music.
After that I can even turn off my Android phone, even shut it down or reboot...music keeps playing.
Simple! Free. No configuration, no transcoding, nothing installed on the server. It just works!
Note, this has no involvement with DLNA or MusicBee.