This will be awesome for another project where I'm using the proper XR manager. On the project at hand, we're still using the older Player Settings XR.
So far as a workaround I'm using some XR custom actions for XR Input (from MIT). 'Set XR Device Transform' has an event option for 'on no device' .. which is working so far. But the awkward part is there's no way to event 'device found' .. so I have to wait a short given amount of time where 'device not found' is NOT triggered, before I active components for the VR camera.
Thanks for the custom action!