I hate barrel jacks, it seems that every single time I encounter one it's different from any adaptor I have. Size, voltage, and polarity can all differ. People got sick of having 10 differnet power adatpters to charge stuff. Hence the demand for "single connector" which seems to have converged on the USB-C form factor.

Right, but if it's not actually USB-C, at best you're looking at the device not working when plugged into a proper USB-C power supply. At worst you're facing fried electronics.

Agreed that would be like wiring a standard North American household wall outlet with 240VAC. Technically possible, but will probably fry anything not expecting it.

I came across a group of racks in the IT room in a (US) factory once that had 208v on their standard NEMA 5-15R sockets.

Their global-market IT stuff didn't care at all. But some of the US-market audio stuff I was integrating came with old-school linear power supplies, and those items cared a great deal.

Have run into that exact thing also, not that the sockets were 5-15R but IEC C13 in a rack CDU. But someone had some adapter pigtails from C14 to a standard NEMA socket, of course that doesn't change the voltage at all. Hilarity ensued.

Or just include a $0.03 pd negotiator in the circuit

My aftermarket android auto display uses the type c connector for power input - wired directly to raw vehicle power. It will not run on 5v. It doesn't negotiate pd either. It just expects around 13 volts right on the power pins, and the supplied power cable does exactly that. It's portable too, which means that some poor person plugged their cable into their phone and blew it up.