As I mentioned above I was holding back the latest 2 raspberrypi-bootloader packages as it broke bluetooth. I told them and they responded with a confusing answer which took me a couple of days to figure out what they meant and at the same time I was having to put out some other fires:
“The only change vaguely UART-related - at least on the firmware side - in the last week or so is the removal of the code that automatically converts an old cmdline.txt reference to ttyAMA0 to ttyS0 in the event that ttyS0 is the primary (console) UART. All new images for years have used “serial0” as an alias, and now all cmdline.txts have to either do the same or get it write and use ttyS0.”
Long story short I tried several combinations with cmdline.txt and the attach-bluetooth service. arch-arm uses ttyAMA0 in the /boot/cmdline.txt file and this has to be changed in 2 places in the file to have bluetooth:
console=ttyAMA0,115200 ==> console=serial0,115200
kgdboc=ttyAMA0,115200 ==> kgdboc=serial0,115200
The latest 2 raspberry-pi bootloader files has been pushed to the unstable branch when the mirrors sync. Be sure to make the 2 adjustments above in /boot/cmdline.txt to have bluetooth.
raspberrypi-bootloader 20210208-1
raspberrypi-bootloader-x 20210208-1