Free will isn’t worth worrying about in the face of the fact that you can’t reasonably prove that anything at all exists outside of your own thoughts.

You can’t prove that your existence is anything more than the hallucination of an isolated brain - which doesn’t imply that your brain bears any resemblance to your concept of what a brain is.

You can’t even prove that you’ve existed for any longer than the length of your current thought. All of your context is memory, which could equally be hallucination.