My soundtouch 30 units are all connected through my home via airplay 2.
Since the old Apple Airport express A1392 can be updated to firmware 7.8 it now has Airplay 2 compatibility. You can buy AE units now for $40-60 so I have one velco-ed onto the rear of all my Soundtouch 30s then a tidy audio patch into Soundtouch Aux In. Because the AE & Soundtouch both have a fig8 power socket I even found a 'tidy off the shelf' power split cable.
It would be better if BOSE valued repeat customers, because winning greater market share is more expensive than retaining existing customers. But my own solution gives me streaming throughout the home, siri volume control plus ability to isolate any room to their source preference by selecting away from aux in for that room.