It is a philosophical question whether any true randomness exists. Even at the quantum level there is some debate

There is some debate, but the overwhelming majority of the scientific community has accepted that there is true randomness.

(see Einstein's famous quote "I, at any rate, am convinced that He does not throw dice.")

Smart as he was, Einstein didn't offer any other explanation for things that quantum mechanics explains.

I think his rejection was based on the old mechanistic view of the world, which assumed that given enough information and the correct formulas, it is possible to exactly predict everything.

There is a saying that major scientific theories don't get accepted by convincing the opponents, but that the opponents die out in the end. That's what happened here too.