jock

Hello, I neither have the boards you have nor the AP6212 wifi chip in any of my boards, but I can tell you that bluetooth is generally quite a beast.
I have had experience with AP6330 and AP6334 (a clone, actually) and spent countless hours trying to sort things out.
 
First of all, the bluetooth adapter on the same chip of the wifi, but is actually a separate device. The wifi part is connected to the system via SDIO bus, but the bluetooth is connected via a simpler UART serial port.
The dmesg logs you provided are not showing anything related to the bluetooth hardware part, but just some software modules/components, you should provide the complete dmesg log (please put them in a spoiler section), because things happen in out-of-order fashion when device are initialized.
 
Anyway, if you are very very lucky, running hciattach is everything you need:
/usr/bin/hciattach /dev/ttyS0 bcm43xx 1500000 the program will not put itself in background, and you need to keep it running if you want to access bluetooth device. In case it works, you may want to create a systemd service or a script that runs at boot.
Change ttyS0 with the serial port your bluetooth adapter is internally connected.
You may need to put the right firmware file in /lib/firmware/brcm, I don't know which one is required so you have to discover it by yourself. Maybe it is already there.
 
In case this does not work, debugging may take ten minutes to several hours/days and unfortunately requires quite a knownledge to deal with.