I'm surprised he had problems powering it up. USB PD will start at 5V as a safe default, and remain there if it cannot negotiate a higher voltage. My Rock5B run

I'm surprised he had problems powering it up. USB PD will start at 5V as a safe default, and remain there if it cannot negotiate a higher voltage. My Rock5B runs fine at 5 volts from "regular" USB-C. When I fully load all 8 CPU cores the board wants about 1.6A (~8 watts). Perhaps Geerling's power adapter refused to provide anything without bilateral PD presence.