the technical specs of the 5B+ on the website state that this is a valid power source:
Power adapter with fixed voltage in 5.2V to 20V range on the USB Type-C port
if i understand this correctly, this means that you can directly wire up a 5.2V - 20V power source with just the VIN & GND connected instead of using PD (on the USB-C PD port)? sadly this is not confirmed in any of the documentation i could find and it seems completely out of spec for USB (which should be 5V/2A without PD / QC which in turn requires a protocol to be implemented rather than just feeding it the higher voltage directly).
is this a safe and acceptable way to power the 5B+ with something close to 20V over the USB port without PD?
i did find this post though which seems to confirm it for the 4B: Powering Rock Pi 4b directly from car
as a suggestion for future boards: it’d be great to have a VIN pin to connect to (in addition to the existing 5V & GND pins), as is e.g. present on Arduino-compatible headers (also e.g. STM32 dev. boards)