I'm a hard determinist. The everyday physical world is clearly causal and I can't think of any particular reason to suppose that we aren't also.
Free will is like red. It's something the brain creates because it's useful. There is no such thing as red; it's just an internal label the brain creates in order to quickly identify different EM frequencies. It's fast and useful, but it's not true. Free will is a short cut that enables us to navigate a complex social world, quickly and create stable social units.
There are academics who subscribe that free will is compatible with determinism, which makes no sense to me. They talk about free will as an emergent property that becomes independent of its constituent parts (neurons, body, environment). They talk about "top-down" causality, where organisms and organ systems constrain the behavior of their constituent parts, like neurons, cells, molecules, atoms, etc.
It must be bullcrap. I think the correct way to see it is that nothing is constraining anything. The mind cannot constrain the brain's neurons to do anything that they must not do; otherwise it would be breaking the laws of physics. Top-down causality is impossible. It's nonsense.
I wouldn't say down-up causality is wrong, but a better way to look at it is that the top isn't constraining the bottom and the bottom isn't constraining the top. Rather, life and organisms can be seen as matter swirling through torrents, and momentarily getting stuck in loops. Our constituent molecules are being hurled around like eddies in a stream. Our molecules are stuck in a temporary dance. It's complex, yes, but also entirely deterministic. Nobody's constraining anybody and nobody is breaking any rules.