As Guyomech pointed out, this has been debated in the Nexus more times than I can count, and seems that we are still far away from any possible consensus. Not just nexians, but humans in general. But to reply to your question and contribute to the (controversy-free) statistics...
I haven't had so far any type of entity contact using DMT. That said, I have encountered presences with other substances. And my views on this would require a third way, or better than that, reformulating the question.
Eliyahu said:
I personally believe they are real aliens. I see no reason to "pretend" that it's just all in my mind, to me this is a form of hiding. of course this is only my opinion. Nothing more.
Eliyahu's experience and the words he uses come straight to my point, since it's in words like "real", or in expressions like "just in our mind" where the trap lies IMO.
We have grown in a strongly dualistic cultural frame. Plato the greek opened fire his cave myth, where he suggests we only see shadows, reflections of a superior, unattainable reality. Ideas are perfect, the material world is imperfect. Also adopted by christianity, Descartes spoke a lot about the separation of material body and immaterial soul (funny, though, how he believed body and soul interacted in the pineal gland). He was the father or western philosophy.
I think we have to transcend that frame of mind. And when people says that something is less real because it "only happens in the mind", they actually imply that the mind is a secondary actor, something contingent, a byproduct of our circuitry, and that only consensual facts are to be considered "real". As soon as you question that point of view, you also are starting to question the classic "real vs. non-real" debate.
The concern behind "are DMT aliens real?" seems to be rather "should I consider them as facts in my daily life?" or "should I re-make my map of the world because of my experience?". And to both I'd answer a big YES. And that YES is independent from the consensual reality of one particular experience you had on DMT. Look at it this way: Whether you are somehow witnessing a distant, trans-dimensional reality that you cannot access with your physical eyes, or your circuitry is constructing this amazing reality, providing it with qualities and sensations that go beyond anything you could imagine so far, the implications are equally mind-blowing. And we try to fit psychedelic experiences inside of our coherence-constructing cultural device, but if there's anything psychedelics show us is the social straight jacket that device can be.
Is the Universe the mystery, or is it your mind?
I do not need to pick. Since I don't even know if they are different things at all.