As a similar question was deleted by its owner while I wrote up the answer, I decided to share it this way.
I have a Samsung SmartTV, and want to use my Android device to remote-control it – including switching TV channels, adjusting volume and, if possible, the full spectrum of features the SmartTV offers. My Android device does not have an IR blaster, and I'm not speaking of "buying additional hardware" for it.
Is this possible – and if so, how?