Graphics raycasting if renderer in game object is seen and not occluded

I understand there is a way to test if something is within the bounding box of a camera frustrum and also how to physics raycast it. But, how do you check if a game object is seen or not (including cases of occlusion) - without using a physics collider?

Do you mean something like this?:
“OnBecameInvisible is called when the renderer is no longer visible by any camera.”