Update to 2021.2.16f1 breaks XR

Unity Engine
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1

I just updated my project from .6f1 to .16f1, and updated the XR package to the latest.
In non-VR mode everything is fine, and I get ~90fps while playing with the editor open. However, if I enable XR, it runs at less than 1fps, and after a minute Unity exits with this:
8013473--1031408--upload_2022-4-1_21-54-0.png

I ran the profiler once and it reported 98% of the time spent in Profiler.FlushMemoryCounters. The other times I haven’t been able to run the profiler before Unity exits.
I am using URP and OpenXR.
Anyone know what the problem might be and how to fix?

2

I re-opened my project in .6f1 again, and reinstalled the URP, OpenXR and XR packages. The problem remains! Now what…

3

I restored my backup, and it too is broken. I now have no working VR for my project.
I can create an empty scene and it runs at 0.1fps