I recently decided to switch to a 2x2 TB SSD RAID drive running in an enclosure off of my Mac mini, replacing an old but not-yet dead NAS.  The NAS did backups and held my music files.  I found such cheap (Intel) SSDs that the whole thing came it at about $200, which is cheaper than a comparable NAS with mechanical drives.  It seemed pretty simple to swap, with OSX Extended (Case sensitive, journaled) format partitions for public files (music), Time Machine, and Misc on each of the two RAID drives.  Time Machine loves it, and I can read and write to the other partitions as normal.  

Sonos, not so much.  When I specify the path to my music, e.g., /Volumes/Pubic RAID/Shared Music/iTunes, I get maybe 10 seconds of indexing (lots of music, so it should take a long time even off of a fast SSD) and then no music in either the Mac or iPhone app.  

If I do the same process off of my base HD, which is a tiny SSD that is APFS formatted, it works (for the 10 or 20 tracks I have there).

I’d deeply appreciate any help the group could offer.