That is however, very disappointing, as I and others have been waiting for over 4 months for this to be added into the Unity SDK. In earlier posts it was mentioned that it will come in the March 2019 update.
So how long now do we have to wait before we can see and enjoy this new feature of instant preview?
And yes, I would gladly test it out for you when you have a pre-release (Beta).
Thanks for keeping us to moving forward to the better way.
We currently are investigating new method and try to enable the preview on HMD side, however there are lots of factors we need to handle carefully like performance and effect/impact when we also enable new features like single pass rendering, foveated rendering etc.
I'll update here our study result on the end of April, and definitely we're glad to share our beta version for your trial in advnace to make the functionality even better and robust.