Would the designers want us to know?

If they're powerful enough to build a universe simulation, theoretically they can blur the edges so we can't discover them. They might even be able to construct and limit the systems of maths and physics we have access to.

I suppose the simulation could be smaller than a universe simulation though - and this is actually really compelling -

It could just be you that is simulated.

Maybe your consciousness and sensory inputs are simulated. You're kept largely on rails and the rest of the world is run at lower fidelity. They know you won't go poking at particle accelerators and theory, so they can keep those pieces low effort and you just get fed narrative. The only things to simulate are those that are directly in front of you now.

Almost like a movie. Not a universe at all.

We might have that capability within 50 years. All your sensory input being simulation. And the virtual brain playing with that input or replaying recordings.

That could be totally feasible. And we might have that tech soon.