I appreciate your help and found my missing RASPBERRYPI_BOOTLOADER_IMAGE might cause the issue. I wanted to add that but one question arised that I could not answer by searching in the doc.
Where is the custom u-boot built, in my case for the raspberry pi with 64 bit? I could only find information for Yocto based images where presumably a custom u-boot is built.
I checked the resulting image that mender-convert created and the u-boot is still the same as in the “stock” input image.
As of now, I have been fighting Mender and Ubuntu Server versions (20.x and 21.x), but have not been able to get a bootable image. The latest status is:
Fresh Ubuntu 20 Server x64 on RPI4 install
Shutdown RPI4 and modified partition structure to match Mender’s expected layout (not sure if this is needed, just grasping at straws after a month…
Booted RPI4 again to confirm new layout did not bork the system. Shutdown after confirmation.
Note: Other options used in the past included the use of the sparse option to speed up imaging. This did not seem to matter, but it could be counterindicated, I do not know.
Resulting goldenimage.img converted without customizations in config files, and the conversion process completes without unexpected warnings or errors (size warnings and other items were expected).
Image written using dd using reverse of previous process.
RPI4 booted, but nothing occurs. Black screen from display output…