Reading the other thread with this subject title, reminded me of something similar that happened, although it was just a one-time thing.
I have a Pi 4 from an official kit, with official power supply and it works fine. Has for quite some time.
Then...
The other day, I decided to do an update/upgrade and during the upgrade, a window popped up saying something about a new desktop config having been loaded and that to install it, I should reboot. Note that no new kernel was installed, so, technically, a reboot was not mandated. But, I decided to go ahead and reboot anyway.
On the reboot, the main HDMI screen came up black (no GUI, no desktop, nothing). The secondary HDMI screen came up normally, but, of course, did not have lxpanel running, so there was no way to get a shell open. I was (luckily) able to SSH in, though.
After waiting a while and verifying that nothing significant was running, I was able to "sudo reboot" from the SSH connection and it rebooted normally, and everything has been OK since. But I'm really curious what happened.
Note, BTW, that I had done "the eeprom thing" (details at: https://jamesachambers.com/raspberry-pi ... ery-guide/) a few weeks ago, and I'm running the latest eeprom now (September 10th). I mention this because on the reboot after the eeprom upgrade, there is a period of "black screen" where you just have to be patient (and, presumably, panicking by either rebooting or pulling the power would be disastrous). My first thought on seeing the "black screen" in the current instance was that it was doing another eeprom upgrade, but I'm pretty sure that wasn't the case. As I said, eventually, I just went ahead and rebooted (and it all seems to be OK).
Any ideas what happened here?