Did Einstein ever say that QM is non local, and therefore it is wrong? The discussions around this topic seem to imply this, but I don't know if this happened. Also, AFAIK what Einstein really didn't like, was the idea that, at a fundamentals level, our reality isn't deterministic. This is at odds with our everyday experience, but it seems to have been confirmed by experiments. So maybe focusing on what their thoughts about locality were could be missing the forest for the tree.

I added the link to Veritasium. They discuss what Einstein said, his exact words. They even show books where his words were printed. Though in German ofc.

Veritasium tries to uncover all the story of the myth of old demented Einstein who was unable to accept QM. And it seems to be a very unfair myth. They say "the history is written by victors" (in this case by Bohr), and I tend to agree.

> Did Einstein ever say that QM is non local, and therefore it is wrong?

Well, kinda, but not exactly. He said that Copenhagen interpretation of QM is non-local. Not QM itself, Veritasium cites some Einstein's letter to Bohr where Einstein explicitly accepts the math of QM, because it works, but opposes "spooky action at distance". Should we interpret it as Einstein claimed that QM is wrong? I'm not entirely sure, he hoped that if they fixed that non-locality thing of QM, they will be able to bridge QM and GR. (Probably, his previous experience of fixing non-locality of Newton's gravity led to this prediction.)

You see, Einstein had one wrong presumption. He thought that if QM non-local then it would lead to contradictions. But it turned out that it doesn't lead to contradictions: a measurement and a wave-function collapse lead to non-local consequences, but they cannot be used to transfer information. So no contradictions. Despite this wrong presumption, I didn't hear Einstein saying QM is wrong, he was pretty careful about what he said, and you'll probably can't catch him on a single wrong claim. He pointed to non-locality and said "it smells". He proposed hidden variables as an alternative removing the smell. It is all. None of these claims were wrong.

I believe he was seeking some thought experiment that can show contradictions, but he failed. But he had found experiments that can show non-locality without any doubt.

> maybe focusing on what their thoughts about locality were could be missing the forest for the tree.

I don't think so. It fits perfectly. Einstein spent ~10 years fighting gravity, mostly due to the reason of non-locality of Newton's gravity. Non-local gravity couldn't work with relativity, it leads to contradictions. Einstein fought non-locality for 10 years, and it fits perfectly that he noticed non-locality in quantum-mechanics instantly, when others didn't (it was even not because Einstein was a genius, he was just primed to non-locality and highly sensitive to it). It fits perfectly that Einstein was very concerned by it and sought ways around it.

For example he proposed hidden variables as a way around it. Just think about it: his hidden variables didn't try to make quantum mechanics into a deterministic theory, values of hidden variables meant to be non-deterministic. Eistein tried to make QM local, by fixing hidden variables way before "wave-function collapse".

At the same time your claim that Einstein was against non-deterministic nature of QM, doesn't fit facts, AND it fits perfectly with people not really understanding what Einstein think is wrong with QM. Bohr had written an obscurantist's answer to EPR paper, in which he claimed that he won the dispute, but I'm not sure there was at least one person who really understood how. This smog of war naturally leads to people hypothesizing and coalescing to some easily understandable hypothesis. And hypotheses of Einstein's aversion to non-determinism is an easily understandable hypothesis.

So my (probabilistic) judgement is: the story told by Veritasium is highly probable. It relies on some sample set of facts. The sample can be non-representative, but the whole story fits in a way that I don't believe anyone can fit artificially, even if they tried really hard.