>>11497944>is quantum mechanics really randomYes, the theory is a probabilistic one. Even if you're a hardcore MWI person, there may be no black-box RNG, but the way you distinguish which "branch" you're on is through (essentially) Bayes' rule.
Now what I think you're really trying to ask is whether QM is the full story. Obviously it's not, but whether that "full story" is still probabilistic in nature... Diplomatic answer is we simply don't know. I know a lot people like to comfort themselves with just saying that, well POVMs are just effective interactions between a macroscopic environment and the microscopic quantum state, so they will always only be modeled via statistical approaches. But deep down inside, if you could track every single degree of freedom in the environment and system, it'd be nothing but unitary dynamics, baby.
It's a nice tale to tell, but I don't buy it fully. My personal, worthless take is "yes". Simply being that Bell's inequalities (and contextuality more generally) require us to give up either locality or realism. Well QFT takes locality very seriously and it has been quite successful in predicting experimental results; besides, I was never a big fan of realism to begin with.
