As I reported yesterday, 2.9 MT took a dump on me. 2.8 MT was fine. Dug around the ED forums and this post seems to work for most, if not everyone. It has cured my 2.9 MT problems. TLDR: Parked CPU Cores is the culprit.
I’ve got the i9 13900KS which has 32 cores. Before I ran the app, 22 cores were parked! Now, all are unparked and DCS under 2.9 MT works flawlessly with DLSS.