Is Deckard an android?
The answer is yes.
The movie works either way, so choose whichever belief works for you. You can change your mind and swap, midway through the movie, or you can watch it again and think the opposite of what you did the first time, you can believe both are true at once, it really doesn’t matter.
That’s how good it is.
The book, in which he definitively is not an android, is even better. But not because of that.