I've rebooted my computer almost ten times just now. Something was just wrong with it and I couldn't understand what.
It booted fine but then when I logged in the display just straight up died. I tried to boot into recovery mode but couldn't remember the root password. Then I tried booting from a live USB stick and couldn't understand why that didn't work until I realised that the ubuntu install on the stick was 64 bit while my computer only has a 32 bit CPU.
But y'know... It was obvious that I'd messed something up. I just didn't have a clue what. I decided to give it up for the day; I can reach my fileserver from work, and I have a backup of my keepass file there with the root password saved in it.
Then it hit me. A couple of days ago I was tinkering with the power saving settings and nothing seemed to make a difference. I'd pulled the levers all the way up and down and turned booleans on and off to no avail. Now, after a reboot, it had taken effect. In... uhm... some sort of state.
So I logged in again. And hit the hotkey for increasing screen brightness. Lo and behold. I could see my desktop.
Apparently I had set the default display brightness to 0% 🤦
-- CC0 Björn Wärmedal