@rosenfeldpj
Often both of them are within the same chip, thus the same firmware, and sometimes even use the same antennas! 😉

I made many test, it seems that dialer app can't use BT.

the phone ring sound is in my BT device but if I pick up the call
the speaker is enable and bt disable instantly
when I hang up the phone speaker instanly disable and BT instanly enable.

perhaps /etc/pulse/default.pa can be modified to "force"bt all the time? but I don't
find solution.

@rosenfeldpj One question, if the phone is new and comes with android 9, do I have to change to the other android 9?