I own a Synology DS214 and works flawlessly with RuneAudio in NFS.
My configuration is
- NFS enabled (of course)
- NFSv4 support: disabled
- under Advanced settings, I have only "Apply default UNIX auth..." checked
To correctly mount the folder where my music is (in my case "Musica"), the right "Remote directory" path to specify in RuneUI is "
volume1/Musica". Specifying the right volume is really important, otherwise you won't be able to mount your folder.