Alternate facts is a fascinating phrase and idea. To me, alternate facts is like experiencing a blinding snowstorm while laying on a sunny tropical beach. It can be distracting, to say the least.
Alternative truth. This is also fascinating. This is to say that truth does not exist, or perhaps that it is completely and totally malleable as to not even be what it was first thought to be. Truth is or is not. Otherwise, truth may only be a personal viewpoint, as in a truth and my truth. If there is really truth, it would be truth and anything other would be not truth. This would make alternative truth a misnomer.
Alternative reality. Reality is or is not. Yet reality is not one of those things that can be absolute. All reality, including so-called alternate reality would be the reality of the source of the recognition of that reality.