I also encountered the same situation. I wrote the Ubuntu Orange Pi 5 Max image from the Orange Pi homepage (http://www.orangepi.org/) and it ran normally, but when I wrote the Armbian Ubuntu version from https://www.armbian.com/orangepi-5-max/, the indicator light was only green and nothing appeared on the screen.
I also tried writing the Armbian version for the regular Orange Pi 5 or Orange Pi 5 Pro and it could run (although wifi and usb were lost, but I could boot to the desktop), but when I wrote the Armbian version for the Orange Pi 5 Max, it did not run.
Is it a bootloader problem?
