I was playing around with mixed reality over a year ago, was not aware oculus could do it now. Takes a long time to do, might have continued with it but you really need a dedicated green room for it which I don't have. I am not sure what you are doing but good luck.
I'm working on this now in 2021. Anyone solve it? I'll let you know if I figure it out. Mine looks flipped left to right and front to back so possibly a rotation about Y (about "up" in Unity). Also, the MRC app does seem aligned (visualizes controllers aligned correctly with the actual controllers) but SuperHot has the flipping issue. Still trying to get any of the other MRC supporting apps to detect the headset.