If we agree that everything we see is described by physics, then everything including us is simply a computation. And in principle someone can build a machine to carry out such a computation.
People in such a machine will be more or less like us, and the creator of that machine will be exactly like god, outside of space and time, omnipotent, omniscient but having to run the simulation to see what everyone does.
From this point of view creating universe 6000 years ago and making it look billions of years old does not look that insane, just a workaround for finite machine time.
So the main disagreement is not about existence of god, or materialism vs idealism, but whether a human is equivalent to a computation or not.
All of these situations are quite convoluted if you want to fit a designer in there.
But then I realized… whenever I create fake people for unit tests I give them names that correspond to what they do. Could this be a sign that the universe is a simulation? And, that God is just a QA running some tests on it?
So maybe we’re living in an edge case!