None of the teleoperation source code has been released, so you cannot find it at the moment!
Reachy is based on ROS, but the communication between the Oculus Quest and the robot has nothing to deal with ROS in our app. Our teleoperation is done using gRPC (currently moving to webRTC), for the joints command as well as for the camera stream, with the robot being the server and the teleoperation app the client of the gRPC services.
We build the app using Unity, along with Oculus Integration (you can also use SteamVR plugin) to get the input from the VR device.
Then all our data is transferred to the robot through the gRPC services we designed, with the client side implemented in the Unity app.
We are then able to send for example the target position of the end effector to the robot through one of our services based on the position of the VR controller we get in the Unity app.