There’s a lot to unpack in your response, but ultimately it reminds me of idealism (in the metaphysical sense) vs empiricism. People will firmly believe one way or another as suits them, but if even if we didn’t exist to have this conversation (and our beliefs didn’t exist) there would be indisputable and fundamental aspects to reality and existence. What are those, and how do we probe them? I don’t think we can answer this without abandoning the metaphysical to some extent. To me it seems like non-materialist povs just muddy the waters and give a lot of voices to things that sound nice and interesting, but are ultimately just nothing 🤷‍♀️

Also I think it’s necessarily idealism that lends itself to relativism (your point about the aliens and animals) and not materialism. I think for me the crux of the matter is that systems and information contained therein exist with some fundamental properties, and none of that has to do with what we necessarily think of them

Edit to your point about brains: not sure if this is what you were eluding to, but even if you recreate someone’s brain outside their body to the point that both entities can affect each other, it doesn’t change the reality of the original brain and it doesn’t diminish the existence of the replicant. I think there’s enough stochasticity in physical systems that the original and replicant essentially become distinct entities over time despite having some degree of effect on each other. It’s not unlike being with another person, we all affect each other in some way.