I finally got it working!!!!
I'm still not 100% sure how though as I tried so many things, but I think it's this option in the bios:
M.I.T. -> Miscellaneous Settings -> Peg Gen3 Configuration -> Set to Gen3 (instead of Auto).
In addition, I disabled the igpu and set the Init to PEG. Not sure if that was necessary, but I don't wanna change anything in this fragile setup!