I’ve been trying to get bluetooth input working, as posted here. Reading your post, I thought the problem might be enabling the experimental features and installing firmware-linux on Debian but doesn’t help. The problem might be that some sort of signal that the bluetooth device sends when it is ready to record isn’t being received. Pavucontrol sees everything and switching to HSP/HFP does work correctly from what I can tell. I’ve been testing with gnome-audio-recorder and what I am seeing is that when you press record it takes you to the screen you see normally but the time is stuck at zero. Perhaps this can be solved by redirecting audio sinks as seen here, but I don’t know what to connect to what. It would be great if I could make this work but it’s looking like I’m going to have to buy a bluetooth to audio jack adapter 
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