The way I think of it, which makes sense to me and maybe nobody else: Quantum mechanics is completely deterministic. But the point from which we are observing

The way I think of it, which makes sense to me and maybe nobody else: Quantum mechanics is completely deterministic. But the point from which we are observing it is random. (Not our origin in space, but our origin in possibilities.) The spread of a waveform is deterministic, but it seems random because we can't predict from which outcome our perspective will originate. That's why the multiverse interpretation is (imo) the simplest way to reason about QM.