My laptop has
$ upower -i $(upower -e | grep BAT)
[...]
voltage-min-design: 11.58 V
And I can charge it via USB-C using a 22.5W powerbank @ 12V (HP EliteBook 845 G10.)I guess that would be out of spec then?
edit: nvm I didn't see the qualifier 'minimum'
If your laptop's USB-C circuitry were built for it, you could charge it from 5V. (Slowly, of course.) It's not even that much of a stretch given laptops are built with "NVDC"¹ power systems, and any charger input goes into a buck-boost voltage regulator anyway.
¹ google "NVDC power", e.g. https://www.monolithicpower.com/en/learning/resources/batter... (scroll down to it)