I had some initial issues adding my Synology NAS music library as a source. The key for me was that I had to specify ‘vers=3.0’ in options for cifs.Relative to SMB, my NAS is set to: Min SMB Protocol = SMB2, Max SMB Protocol = SMB3
Assuming this is what you are trying to do, here are the details of what I did on Volumio:
Settings → Network Drives → Add New Drive
NAS IP Address: Either IP address or Network Name (both worked for me)
Path: NAS share name/path (the Volumio web app will add the appropriate backslashes. This will result in the @evilmrb full path string)
Show Advanced Options:
File Share Type: cifs
Username: Username for the share, set in the NAS
Password: Password…
Options: vers=3.0