NTLMv2 is decades old and inherently insecure, I can certainly see why companies want to move on from it…. I guess, like Flash player, once a few companies stop developing for it, others will soon follow suit.

Folks have been talking about SMB v1 for years, rather than rehash it all look at the previous posts.

Short: Sonos knows, it is not easy and there is no economic justification at this point.

Many easy and inexpensive work-arounds are possible.

Just move to DSM 7 on my synology and same problem.

For those who find this after moving to DSM 7, there *is* an answer. Actually, I have two.

1. Re-enable NTLMv1 on your Synology Diskstation: https://community.synology.com/enu/forum/1/post/140194?reply=452216 — Obviously this brings with it the security issues of NTLMv1, but it also gets you music library back online.
2. Use Plex. Install Plex on your Diskstation, and let it manage your music library, too (simply point it at that folder and Plex should do the rest). Then link Plex to Sonos and, boom, it’s an even better solution (on a lot of different levels). 

It’s not, though, is it? The Plex implementation for Sonos is rather limited - or was when I tried it.

The web/PC version was much more fully featured, but they left most of this out of the Sonos version.