[jjd-uk]

WOW!!!! Now, FINALLY, theres a TEST.m3u file in playlists > music
Open and compare to iTunes m3u exports.
Kodi -
#EXTCPlayListM3U::M3U
#EXTINF:0,01. Album Name - Track Name  (I suppose this order is because Kodi created playlist from Album)
iTunes -
#EXTM3U
#EXTINF:920,Track Name - Album Name (I suppose this order is because iTunes created playlist from Library list of all tracks)

Change #EXTM3U in iTunes export playlist to #EXTCPlayListM3U::M3U like Kodi CoreELEC playlist.
Kodi frowns and still will NOT play playlist

Replace comma after track number in iTunes export playlist with a period and a space like Kodi CoreELEC playlist.
Kodi makes a face and still will NOT play playlist

Add 0, in front of track number like Kodi CoreELEC playlist.
Kodi sticks out tongue and still will NOT play playlist

SO WHAT THE HECK DOES KODI WANT ANYWAY

You have not provided the file paths contained in the test.m3u you created in CoreELEC which is the only thing that matters.