Macbook Pro 2011 white screen - can't install MacOSX
Thanks to @Allan, I was able to find out how to solve my issue. I did the following:


I had another Mac's SSD be cloned using a program called carbon copy cloner to my Macbook's SSD.
I ran the High Sierra installer on that Mac, specifying the Macbook's SSD as final medium (this added a recovery HD)
Boot into single user mode to tweak the NVRAM using this guide, and this question was also very relevant.
Step 3 needs to be redone every time you update your OS. Note: your brightness function keys will also not work anymore!


Important command for temporary fix:

sudo nvram fa4ce28d-b62f-4c99-9cc3-6815686e30f9:gpu-power-prefs=%01%00%00%00


Transcript of the MacRumors thread in case it get's removed:

First of all, it is possible to successfully boot a MBP to OS X while still using the failed GPU, after you remove the AMD drivers by booting in command line mode (CMD+S) and entering these commands:
1) fsck -fy (to check a disk)
2) mount -uw / (mount a root filesystem with read/write permissions)
3) sudo mkdir /AMD_Kexts/ (make a directory to store the AMD drivers in case you'll need them in future)
4) sudo mv /System/Library/Extensions/AMD*.* /AMD_Kexts/ (move the AMD drivers)
5) sudo rm -rf /System/Library/Caches/com.apple.kext.caches/ (remove the AMD drivers cache)
6) sudo mkdir /System/Library/Caches/com.apple.kext.caches/ (just in case OS X will be dumb and will not recreate this directory, I am creating it for OS X)
7) sudo touch /System/Library/Extensions/ (to update the timestamps so that new driver caches - without AMD drivers - will be definitely rebuilt)
8) sudo umount / (umount a partition to guarantee that your changes are flushed to it)
9) sudo reboot