Yeah, It works in multi threading with steam vr, I was under a misconception and thought openxr only worked with mt and steamvr only opened in st. (I think I also had some misconceptions about openxr which i still dont quite understand)
I'll amend my issue to say I can launch the game through steam vr, but it doesn't work when I launch the game with just the mixed reality portal open as I had been doing in previous versions which worked perfectly fine