We are writing summer 2019 and still Sonos only supports SMB version 1 for the Music Library share.
This is not acceptable.
A file share running SMB1 is extremely vulnerable to all the variants of cryptolocker virus that exists today. File share servers (NAS, Windows, Apple OS) can only support one version of SMB - so you cannot from the same box have one file share (for Sonos) using SMB1 and the other file shares using SMB2 or SMB3. This way Sonos puts each and every file share at serious risc - just because they don’t update their file share protocol to comply with this century.
And for the record - the “solution” through PLEX is not a solution. Unstable at best.