Question about Atomos Shinobi

Yes, the monitor is compatible with the camera. It also needs a corresponding cable, a battery and a mounting device for the gimbel. I doubt whether the latter is available for purchase. If you install the monitor on the fixed part of the gimbal, you need a highly flexible and longer cable, so that the cable does not block the movements. If you mount the monitor on the moving part, you have a completely different centre of mass than with just the camera.

If the 80D has an HDMI output, then yes, otherwise not.