I had this issue too. And although I like SwiftKey, Samsung's keyboard is still better (it essentially uses Swype). But, like others, I think Samsung's Voice Input is terrible compared to Google's. So, I dug a bit deeper. It turns out Samsung disabled Google Voice Input. So, if you set the Samsung kb as the default, Google Voice Input will NOT be available. Your only choices are to use Samsung's Voice Input or to disable voice input altogether (as others have found).
If anyone can find a way around this that still allows the use of the Samsung keyboard, that would be great.
Note to Apple posters - We don't need to debate Siri (or any other Apple product) here. None of us are going to install Siri on our Note 7's (if for no other reason, because we can't). This is a product specific issue on a product specific forum.
Ha! I had placebo effect!
That does it. I'm replacing the stock keyboard. I love Google Voice Input. It's the best.