> you cannot prove that we are not in a simulation, and in a sense it does not matter

I'd consider myself a materialist (in the philosophical sense) and this is why (and I agree with the rest of your comment to)

We can not know, but in the absence of evidence to the contrary (e.g. someone metaphorically popping their head in from "outside" and revealing another layer to us), while it is important to understand that we do not know, it is more productive to assume in the absence of evidence, whether it is "real" or subjective or a simulation.

As long as it appears to us to follow consistent rules, we can explore those rules, and explore our apparent material reality.