2 things I found on a quick search:
1st Look if your GPU is actually designed to have a „headless“ start - if not you most likely need that dummy adapter that others mentioned
2nd In the bios settings look for something like an “Halt on all errors” option and disable it. If the GPU is the problem than you might get to start it anyways without any monitor connected
Hatte die Signal Foundation sich nicht schon irgendwo mal geäußert, dass sie für die Schnittstelle zu WA gar nichts „entwickeln“ möchte!?