Take screenshot with no freezes with Unity or Android Plug-in

Hello,
we're working on a Unity VR experience where a mobile client interacts with the player's VR scene. The mobile client must have a visual feedback of what the VR user is doing, like mirroring. Since this must happen outside the local network, traditional mirroring is not an option.

We are sending screenshots from the Oculus Quest to the mobile client every 5 seconds using our own API but capturing the screen it's not easy:
- using Unity's ReadPixels returns a black image.
- using Unity's CaptureScreen class briefly freezes the VR app.
- using a native plugin return a black image, since the UnityActivity's SurfaceView is always empty.

At the moment the CaptureScreen class is working pretty well but the freezes ruin the experience. If you have any suggestion about how making the screenshot "faster" or achieve the remote mirroring we need would be very appreciated. Thanks.