Only reason you believe there is a mind is because the mind says it exists. But have you investigated where is that mind and who is that which mind if speaking to?
The discussion about the ego and "the mind" and the "who you are" in that sense are then still useful for the human to feel comfortable in feeling like they have agency, and I am aware of Buddhist philosophy in finding peace through detaching from our inner voice and gaining wisdom from not letting ourselves being driven purely by what we think we are or "what the ego says we are", but I think it's besides the point in this context (but very useful to include in a balanced "diet of thoughts").
Maybe the ego is an evolutionary defence against nihilistic traits so we all don't kill ourselves by realising none of what we do is any agency and it's all predetermined by the start of the universe. But anyway this part of the discussion enters into a rabbithole detached from the core discussion of there being free will or not, at least to me, because I cannot accept that a core property of the system "universe" and the definition of it's causality or not could depend on the thought process that goes through minds of humans in some remote part of that very universe. A detail about the higher level thought process of some "blobs of particles" in the universe don't define the way the universe itself works. Our relationship to the self doesn't have anything to do with physical reality of if-this-then-that. In other words the causality doesn't care what we think of it, it's either all pre-determined or not, our opinion doesn't matter.