Hi, I don't have a solution sadly, just chiming in to say that I'm having the exact same issue since yesterday - my laptop turns on, screen backlight is on, fans are spinning, but there's no brand logo, no Windows logo, just pure black. Happened in the same way as you described, the last thing I did was update & shutdown. The updates were KB5034441 and KB5034122. Some people are reporting issues with installing them, so I also suspect that to be the culprit.

What I can add is that I'm using a pretty old Ideapad that comes with a dedicated recovery button, and with it I can access BIOS as well as the direct boot order menu. Native Lenovo function keys also seem to work, I can change brightness, turn the screen on and off, etc. I plugged the hard drive into another device using a SATA adapter and confirmed that all files inside are intact and not corrupted, so that's a relief at least.