Can you clarify what we "already know happens"?
Even for humans, it's not clear that "conscious choice" exists and causes changes in state, because we don't know what the mechanism is that can cause a state change other than state at time T-1.
The obvious answer is that pleasure, pain, ideas, memories, etc. all exist to drive the behaviors that are advantageous in evolution.
It’s possible that there’s a deterministic set of gears in how sensation drives behavior, but the role of experience in driving physical action would be at least one of those components.
So if we take evolution as the cause of life as we understand it, then consciousness is at least a component of physics itself.
How does that relate with the experience of decision making? That's a complete unknown. But the simplest explanation is that free will is simple, once we define it as "the experience of making a decision" instead of the traditional, nonsensical definition of "the act of making a decision that is fundamentally independent from prior events". Usually free will is framed as "choice vs slavery", which is a useless definition because choices can't be made in a vacuum.
In other words, of course we have free will: We feel like we have free will, and free will is simply the feeling of having free will. Conscious decisions (if those even exist!) are physical processes just like everything else in the universe.
They also happen in context, not in a vacuum. Whether or not I make another cup of coffee might come down to fundamentally random quantum events, but that doesn't mean there's any chance I get up and brew a cup of steamy elephant piss because I don't have any on hand.
And of course we don’t have free will. We have experience, which fools us into thinking we are in control.
Not sure if you're disagreeing with me, or if you didn't grasp my comment. The quote above is meaningless without defining what free will is and how it can possibly mean anything other than "the experience of decision making".
Decision-making is something that a fully deterministic, non-conscious machine can do. (A motion detector performs decision making based on light input.) Decision-making does not require consciousness. Consciousness is what grants us the ability to experience and reflect on our decision making. It is fair to call that phenomenon "free will."
Defining "free will" as "the ability to make a decision not influenced by our state and inputs (including sensation, memory, etc.)" makes no sense. Decisions are fundamentally dependent on state and inputs*. Any definition of "free will" which ignores that is useless.
Unless reality is more like Everything Everywhere All At Once, i.e., the Everett many loafs model.