What is the internal BT device, and what is the USB BT dongle you’re trying to load?
Bluetoothctl allows switching between different BT controllers on the box.
show bluetooth devices - bluetoothctl list
select active bluetooth device - bluetoothctl select <mac-of-bt-device>
Do you know if CE supports the BT chip in your USB dongle? Blacklisting a module prevents that BT device from loading, it doesn’t disable Bluetooth. When you say Bluetooth is still visible after blacklisting, visible how?