I recently remembered that you can pair a Bluetooth speaker to a Google
Home speaker. I had a spare Mini collecting dust in the closet so I
paired that with one of my Musicflow's. I had to set the delay all the
way up to 200ms for that speaker, but a...
After you reset it and re-add it to the Music Flow network it should
appear in Google Home but it will be at the very bottom as other devices
that are not in a room.
I have a similar issue. 4 LG multi-room speakers and 4 Google home
speakers on the same network. I can cast to an individual LG speaker,
and can cast to all of the Google speakers plus one LG speaker in a
group, but if multiple LG speakers are added ...