I have spent the good part of a week trying different options to be able to mount my music library to Sonos 2. None had worked and I was almost going to give up. and then I had the great idea to use a RaspberryPi 4 Model B and set up a simple samba server (on an external USB SSD drive).
It works a treat and there is no reverting to SMBv1 or anything .. its fast and secure and all of my music is now available .. I am sharing this in case anyone else experiences issues trying to get their personal music library added to Sonos 2
Happy to share the details with anyone else that needs it