Does the vrchat avatar have face tracking or is that only with the vtuber version?
Viewing post in Dommy Dragon | VRC Avatar + VTuber comments
It has ARKit tracking shapekeys on it, so you can set up face tracking using a VRCFury plugin like Jerry's Tools here: https://github.com/Adjerry91/VRCFaceTracking-Templates
And obviously you also need face tracking hardware.
I've tested it with Iphone tracking sent to VRC via OSC before, but I don't own any of the VR headsets with facetracking