The HomePod mini was quickly opened up after release:
6ft Power Cord.
Non-removable, unlike the original HomePod, which could be yanked from the unit with a hard tug.
USB-C on the wall-end.
Ships with a 20W USB-C Power Adapter....
Short answer: you can't
MacBook Pro 2018 with Catalina 10.15.7
My experience is similar to Billie Hawkin's excellent answer above: setting AutoBoot to %00 prevents boot on lid open
However, sudo shutdown -h now did not, in my experience, prevent the behavior. When any key is pressed, the laptop still booted up.
What do service shops do? crack open the case ...