I've just had a read through the workshop manual T6 2016> Brake Systems Edition 09/2019 and the only reference to Brake Fluid specs that I can see is:-
Only use brake fluid conforming to VW standard (VW 501 14).
This manual cover small and large brakes and ABT e-line system as well. All say use VW 501 14 fluid.
When I put VW 501 14 brake fluid into Google it brings up loads of DoT 4 fluids, two of which are my preferred choices, ATE Typ 200 and ATE SL6.
I used to use ATE Super Blue but fecking EU regs put that one out of use.