Anyway, the command «watch» exposed a B&O error I had been lamenting for months now: if I am playing Deezer on all my 3 products, and then tell the A6 to start playing N.MUSIC, and then join the Essence, now all 3 products are playing N.MUSIC from the ML/NL Converter.
But «watch», applied sequentially to all 3 products demonstrates that «Type: NOW_PLAYING_STORED_MUSIC / Kind: playing» still reports as the current song/album/artist/artwork whatever last played on Deezer! B&O fails to update this to N.MUSIC, which should be the minimum, much less to profit from any N.MUSIC metadata. This error is reflected in the B&O app by showing whatever final Deezer artwork, and ignoring the current N.MUSIC.
I had thought the error laid on the app itself, but I guess it is something in the code of the ML/NL: it probably fails to send an update to the network. Sad, if so!