This was designed to work with Unity 2019.3.7f1 and the Vive Pro Eye.
You need to install the SRanipal Unity package, TobiiXR unity package, and patch "EyeTrackingWrapper.cs" in order for focal length sensing to work. At runtime, you need to install and start the SRanipal runtime, and enable eye tracking within the headset.
Aircraft metal textures are from https://polyhaven.com/textures/metal