As this will normally be a headless system, I'm actually looking if I can turn the GPU off, *unless* there's an HDMI cable plugged in. So (at least for now), the GPUs only function is to have a display when I need it for troubleshooting.
With nothing plugged in, modern AMD GPUs will go into runtime PM and depending on the motherboard design either D3hot or D3cold.
D3cold is as close to off as you can get.
