Arandr is for x11 which can make fake virtual monitors which might have been enough for some cards (most require an active signal through the display port or HDMI at boot to turn on)
We do not support x11 because it is dead and that's an upstream decision.
Please refer to my previous post.
You might be able to do something with a HDMI or display port dummy plug which is commonly used for mining or GPU passthrough or remote control of computers without a screen (sunshine server).
And make it so that display is then disabled when it detect the actual monitor is turned on (I know this works in windows, no idea if it works like that in Linux since I have my screens on when booting my PC)