First, we need the universe to not literally just be a function of the previous state and the current time.
Second, we need (and I'm quoting myself from above to illustrate what I meant): "some kind of metaphorical "door" for our soul, or our true selves, or whatever you might call it, to propagate through meaningfully into our consciousnesses".
Lacking the first means there's no way for the second to exist. Supposing the first exists, we then need it to provide some kind of way for the "us" that exists outside of physics or as an emergent phenomenon out of the nondeterministic parts of physics to meaningfully shape what our brain's electrical states make us do.
If we have all of that, we finally have the beginnings of a system in which we can start to try to philosophically assign moral designations to actions and people. Which is think is about 50% of the reason people want free will to exist: so we can punish others for their actions.
(And just to clarify, to anyone not familiar with how people usually debate philosophy. It's all about your presupposed axioms. Things you and your partner agree to be true. This kind of discussion is one that presupposes relatively little, so don't think I'm trying to make political claims about how crime shouldn't be punished or whatever. I'm simply saying that if we presuppose only that the universe is not deterministic, that alone doesn't bring us forward enough to start building a system of ethics.)