I’ve used rbuild to build a bullseye release with a kernel I built via bsp (the latest mainline so I am aware there may be bugs).
My board boots and I’m able to login via serial console (no network as the r8152_dkms would not compile).
There is a green flashing led on the compute module. It flashes quickly twice, then a pause before flashing quickly twice again, and this repeats. What does this mean? The main ring of led is a steady blue colour, not very bright.
Can you confirm where the 4 pin power header is:
“DC 5V on 4-pin header”
Is this on the GPIO?
Regarding the GPIO, can you confirm the order of the pins, it’s not marked on the board.