Our current understanding is not enough to state that with confidence. We used to be so confident with classical mechanics and even claims that physics is almost complete. God knows how long our current probabilistic model will last before we find another better model. It may be probabilistic, or it may not.

Random behavior of subatomic particles doesn't make free will any likelier either though.

If they act at random on a makro level their randomness would average out to zero. And that actually checks out, since the mechanical forces of the atomic and molecular level are known, observable, and provable. An apple drops from the tree to the ground, every time. Causality is still a thing, even if not observable at the subatomic level.

The only way to imagine a subatomically based free will would be some mechanic over which we, at will, could change the randomness of subatomic particles to behave in a predictable pattern and on a scale that's grand enough to make the proverbial apple fall upward. Or at least make or synapses do something that they physically speaking wouldn't have done otherwise.

Free will is as likely as magic. In fact it would actually be some form of magic - a volitional breach of causality itself.

Not being predictable by us does not mean they offer free will.

The preconditions are so precise that you'll never be able to get exactly the same results from trying to do the same thing twice - you'll never be able to do the same thing twice. But that doesn't stop cause and effect determining the outcome. There is no place where free will can enter in to any equation at any micro or macroscopic level and just having unpredictable microscopic events doesn't give you control of your own destiny. This is totally separate from your own perceptions of having choices you make. Personally I find myself doing things I didn't consciously choose to do. Once you start noticing them you might find more and more.