So here is the supports answer:
Thank you for contacting Aspyr Technical Support!
SWTFU: USE PC is only supported on desktop GPUs.
We can only recommend turning down the in game AND desktop resolution to 1024x768 or lower and deselecting the High Detail checkbox from the initial configuration screen.
Feel free to contact us with any further issues or concerns.
Aspyr Technical Support
So now I've asked them whether I can claim my money back on the grounds that Steam actually does not state that the game only supports Desktop GPU'S. Let's see how that goes.