Indeterminism is not compatible with Eternalism! One thing is to claim epistemic indeterminism to justify compatibility and quite another to absolutely posit the world can be undetermined and at the same time assume all Reality is finished and complete which includes all the future state of affairs. We are talking here about fundamental indeterminacy not epistemic indeterminacy which totally different!
The Multiverse hypothesis doesn't change the picture at all!
The fact that you don't know on which future Universe you will end up being when you are about to make a choice and haven't made up your mind yet is an Epistemic problem.
A Multiverse where all possible state of affairs, all possible Universes exist is Deterministic period! If you don't like cause and effect in an Eternalist set use perfect correlation instead!
I have used this coinage here on A2K for a decade now, and probably most people never had any idea on what I was on about...look this episode that Sean Carol brought about with a modern Metaphysician makes it crystal clear!