It's impossible to actually know whether or not we have anything approaching free will.
We could be a simulation, there could be an omnipotent deity, we could be the product of a bunch of processes unique to ourselves.
None of it matters.
We can only act on the world as we perceive it.
If the world is controlled by some outside force that can manipulate it at will, including our perception and memory of events, there is nothing we can do about that. We are merely constructs under something else's control. If we were ever capable of "piercing the veil" so to speak, the controller could just roll us back to when we didn't know. If gravity was too much, they could change it. Etc.
However, we're going to do our best to understand the world as perceived. And that's the best we can do. We have to operate as if the universe is not being arbitrarily modified according to unknowable rules.
And it's not like any sort of record will prove that it's not. Because the capability of creating this universe also includes the capability of altering the past as well as the present and future.
Similar with free will. Like I explained elsewhere, if free will does not exist, then you can either be persuaded by an argument or not. For any position. Maybe you're predestined to like Joe Dirt. No matter what anyone says about it. You don't get the choice.
Same thing regarding the concept of free will. If it does not exist, you don't actually have a choice in whether you can accept that it doesn't. Either you're predestined to believe in it or not. Because all of your actions are the results of the forces that act upon you, all of which are also the results of actions, etc, etc, all the way to the initial big bang. That one moment essentially wrote it's own epitaph as everything goes back to that moment. Without free will, me writing this and you reading it isn't a chance or coincidence, it's just the result of the forces from the big bang.
So. If free will doesn't exist, it doesn't change anything. Because we cannot change the path we're on. We have no choice. Even if you say, "Yeah, well, I'm going to do X and save the world". Well. You were going to say that in response to this post. I didn't convince you anymore than any other object in motion "convinces" any other object it collides with to change direction. It's what always was going to happen.