MBP Failing GPU how to fix without any Display output

I have another MBP 2011 here with a failing GPU. Normally i edit the EFI with a Linux-Distro and than remove the resistor to disable the GPU. According to this blog: https://realmacmods.com/macbook-2011-radeon-gpu-disable/

But this one does not give any output on the screen. It just stays black. So it is quit hard to give all the commandos. So what can I do?

First i thought about using an USB-GPU compatible with Arch-Linux. But i don't have any atm.

Than i thought about trying using Target-Mode. But is it possible to edit the EFI on the target machine? I would start the Arch-Linux on another MBP and connect the failing one via Target-mode. But what than?

 

Update: I tried to boot the failing into Target Mode, but somehow it won't. It always starts the OS from the hard disk (clearly can hear the old hard disk). I tried FW800 and TB cables.

The OS loads on the failing. I can use the F11 and F12 to hear the sound.

So i going to try remote desktop first.