The plan was to utilise ESP32 hardware with the Espressif HFP stack to do all the Bluetooth heavy lifting. [Jouke] did find out the hard way that this is not a commonly-trodden path in hackerland ...

See Bluetooth. Supports mono and stereo audio. For example, a smartphone transmits MP3 music via A2DP and phone calls via HSP or HFP (see above). See Bluetooth audio. Internet IPv6 connectivity ...