Hi @NicoD Nice to hearing from you here (beside Youtube )
The board is NanoPi M4 (just M4, neither M4B nor M4V2) and I have removed all other peripherals during my testing, only usb keyboard, usb bluetooth dongle for wireless mouse, and hdmi cable for 24 inch monitor.
I have tried below two images and both have issue for reboot, apt upgrade would upgrade it to 5.9.11 but the reboot command doesn't work for me either.
https://mirrors.dotsrc.org/armbian-dl/nanopim4/archive/Armbian_20.11_Nanopim4_buster_current_5.9.10.img.xz
https://mirrors.dotsrc.org/armbian-dl/nanopim4/archive/Armbian_20.11_Nanopim4_buster_current_5.9.10_desktop.img.xz
So after installation, the first boot works good, but after that, if I "sudo reboot" in terminal or click reboot button on the GUI (if it's the image for desktop), I can only see black screen showing on the monitor, no led flashing on the board even, and the board never boots up again. It seems the reboot sequence would power down the board but doesn't power it up again.
I think it's not hardware problem, as below old Armbian image is working fine in the same testing environment, "sudo reboot" could reboot the board correctly, but it has been working for a long while I was thinking to do an upgrade to newer image.
Ubuntu Bionic with Armbian Linux 5.2.0-rk3399
OS: Ubuntu 18.04.5 LTS aarch64
Kernel: 5.2.0-rk3399
Which board have you been using to test the images, M4, M4B or M4V2, and which image have you been using?
Thanks,
Jason