I think free will is a bit like a sphere. There is no true sphere in nature, only a more or less accurate approximation. Likewise for free will, there is no such thing as true free will (tm) but there are better and worse approximations.
Likewise, our pseudo-free will is probably more than enough for having near-independent agency from the environment. Anything outside of that is probably already within the realms of metaphysics, which is unprovable by definition anyway.
And just like free will, there are no true RNGs, just RNGs that we don't have the accuracy or computer power to predict. Quantum mechanics may disprove this.