As reported in many other topics apparently it's still necessary to use SMB1 for playing music from a Synology Diskstation system? It's now 2021 and I just had to change the settings on my diskstation to allow the unsecure SMB1 in order to be able to add a shared folder to my Sonos music library.
Sonos seems to be closing all topics on this forum about this subject for further comments, but is not addressing the problem?