This Unity project is a very simple XR interactions tech example that implements grabbing and climbing using Unity's multiplatform APIs. It's not super clean, but it does showcase a fully physics-based XR Rig.
Unity version 2019.2.0f1
This project targets "roomscale" VR. As such, it meant to be experienced on a HTC Vive, Oculus Rift, or Windows Mixed Reality Immersive headset. It should also work on any other roomscale headset that is supported by one of those SDKs in the future.
You can read a bit more about Unity's multiplatform features here: https://blogs.unity3d.com/2018/11/22/multi-platform-vr-features-in-2018-3/
You can read a bit more about complicated Rigidbody/Collider setups in Unity here: http://jackpritz.com/blog/unity-colliderrigidbody-setups-in-xr