Get Access to Controller Render Models in OpenXR

Question

I am developing with OpenXR (using the C API) and using mainly a Quest 2 headset for testing (but also other systems), and need to be able to load and render controller models (and preferrably be able to animate button presses etc.). I have previously used OpenVR, where controller models for different vendors are available through a common interface (although only static models). With OpenXR, I am having a hard time understanding how to get access to controller models, at least on the test system. I have found the "XR_MSFT_controller_model" extension, which seems to have the functionality that I am looking for. However, the Oculus runtime does not report this as a supported extension (maybe vendors do not implement each others interfaces? That's one of the things that I am trying to understand). My other test systems are HTC Vive and Valve Index, but I haven't come to testing this problem with those yes. The Oculus runtime is version 1.79.0, and I am using the 1.0.25 version of the OpenXR API.

So my questions then are:

1. Is there a common interface for loading controller models/meshes in OpenXR, and if so, which interface is that?
2. If not, are there separate interfaces for all vendors, and what are they, e.g. for Quest 2?