Fincher is doing Mank for Netflix. Filming to start this fall. As of this typing, Reznor/Ross have not been named as composers of the score, but it seems likely. The only reason I have any doubts is that this is a black and white biopic that will mostly take place in the 1930s and 40s. Not the type of subject matter that one would associate with an electronic score--and maybe it won't be. By the way, TR has stated his admiration for the Taxi Driver score, composed by Bernard Herrmann, who composed the score for Citizen Kane.