The sound of conviction in your first sentence does not match the "theorized to be" in the second sentence. I recommend that you don't bring a "for all intents and purposes" to a "philosophically" fight. ;)

Or perhaps the universe is a simulation whose prng was seeded with 1 just like golang does

Maybe we're in the first batch of simulations, and the tester came along and asks why they're all identical. The cosmic coder then realises that they forgot to call the function to seed the prng.

Is it though? I’m merely a layperson here so I might be grossly misunderstanding, but I didn’t know determinism had been ruled out by quantum physics. I was under the impression that quantum phenomena was best described using probability. That means there might be an element of true randomness going on, but also that these systems are so chaotic that an observation is going to have some noise, regardless of any randomness at the core. The latter says nothing about how random things are, merely that they appear with some probability, they could be completely deterministic for all we know.