Even when Target Display Mode was a thing, it still required a running OS on the target system. I do love my iMacs, but I spend more than zero time shaking my

Even when Target Display Mode was a thing, it still required a running OS on the target system. I do love my iMacs, but I spend more than zero time shaking my head at the tight coupling of expensive, high quality components that will, eventually, fail independently. Apple generally does a great job keeping the "eventually" at bay. But it's always coming.