LucasWithLidOff is making a good point that all you determinists are ignoring.
If there is no free will and we have no choice in what we believe in, then every theory we believe is right could be entirely wrong and we'd have no choice to believe it
If you had free will, and you chose to believe in something which was not correct, you would still be stuck believing something false. You would have to depend on external forces, to present new information suggesting that your prior belief was false.
In order for our beliefs to change, some sort of process has to take place, in which new information is evaluated, inferences, and deductions are made. The conclusions that we come to will depend on that process.
The unfolding of that process will be dependent on forces outside of our control. One's ability to perceive new information will be dependent on the quality of one's sense organs. One's ability to evaluate, infer, and deduce will depend on the quality of one's brain, and prior knowledge.
What if you find that there are multiple conclusions, which are equally plausible? How are you to decide which one you personally believe in? How are you to make arbitrary decisions, of any kind? You would require a bias.
So:
The initial stimulus to reconsider your beliefs is dependent the external, physical world.
The process through which you change your belief is dependent on the physical structure of your body, and prior interactions with the external, physical world.
The ultimate "choice" you make after processing the new information is determined by an innate bias.
Where does the free will happen? We're stuck with skepticism either way imo, for many reasons.