Does the B&O app allow the creation of playlists across music streamning sources at the same time (i.e. track no. 1 is pulled from Deezer, track no. 2 is pulled from Apple Music, etc.)? If not, I believe that the Sonos app provides this functionality. Will I be able to stream from the Sonos app directly to Beolab 18/19, or do I need some Sonos hardware for the Sonos app to work – if so, then I guess the play doesn’t work…?
or do I need some Sonos hardware for the Sonos app to work
Yes.
(Note, depending on whether the B&O speaker has a line-in, you could use the Sonos “Port” as a front-end so their app would work, yet still have the beauty & sound of B&O. Ask @SandyB, maybe also you could be satisfied with Roon as your front-end which will cross music services — just not the two you named! — and AirPlay the results to certain B&O speakers.)
.
.
