In reply to: Are any double rifles made with a selector that enables you to switch the ejectors "on and off"
John Rigby fitted a tensioner screw to to the ejector springs in the forend iron that allowed the force of ejection to be adjusted, from full to zero, effectively converting it to a non-ejector. A very simple device, which surprisingly wasn't all that popular.
There are many situations where a non-ejector is preferable. For example, Tiger hunters in India, preferred non-ejectors, since the sound of the ejector often betrayed their location.
With practice, a non-ejector can be reloaded almost as quickly if the gun is allowed to rise with recoil and the gun opened while the barrels are vertical.
I prefer non-ejectors for quail hunting, since quite often the whole covey will take off at the sound of the ejector ping after the rise of a single bird.