Newbie: 3 probs with use; m3us not found, Artwork missing, _Sort Order

[Steve Bullman]

Looking to move from Sonos S1 control app. 

Trying out the app on my tablets (Android 6) and my Samsung phone (Android 12).

All my mp3s have embedded .jpg artwork in every track, each around 30kB.

I use playlists a lot, filed in same artist-album-tracks tree-file structure as my mp3s, all located on my NAS, all setup/accessed via PC.

The playlists are all "relative", so can be moved if the artist chunk of the tree has to be relocated.

Can see the mp3s, and can cast them to the Sonos units OK.

Understand that I will need to keep Sonos S1 app to structure groupings.

But am having these consistent problems:

1) It is not seeing ANY M3u files in the music file store

2) Artwork display is blank

3) On my PC file explorer, files beginning with "_" (underscore) are displayed at the top - so I have many hundreds of folders using this to force them to the top of the listings.

Hi-Fi Cast puts these at the bottom. Could there be an option to reverse this ?