Is it possible to scan specific folders for music files and import them to some android media player app, which could then stream the music to a DLNA device?
Another challenge is that the music files are on a NAS device, so they would be accessed through an SMB share (or AFP, or NFS share, if that changes anything).
I found a way to mount it to android's filesystem (using command busybox mount iocharset=utf8 -t cifs -o username=guest,rw,noperm,iocharset=utf8 //192.168.0.106/xxx /data/media/0/xxx
), so apps see it as a local folder (you must have root for that I think, also the kernel should support cifs filesystem, and apparently the android device should not be in battery saving state and iocharset=utf8 is important if you have file or folder names with special characters), but the problem is that many apps rely on android's media scanner service to find music, which probably has trouble scanning the whole mounted folder and the apps do not see all the music files.