So many people are having trouble with getting this going, I've started a simple example project. It's not complete yet -- I only just started it. But you're welcome to look at what I've done and how I did it.
I intend to show how to get it working with a Quest and a Rift -- I don't own a Rift S, but I assume it's the same as a Rift, generally speaking.
Again, let me say that I'm not finished. But you can see an early look here.https://github.com/Corysia/Unity-Oculus-Example