It is sufficient to demonstrate that I have not the freedom to choose right now what my breakfast yesterday was. If the future is just as factual as the past, then I have just as little freedom to choose right now what my breakfast tomorrow will be. If “free will” means something while the future is fixed in this regard, then it means something other than an ability to change the future in this regard.
Frankly, I do not understand what the argument can possibly be here. We are entertaining a hypothetical, where future events are factual enough for the logically possible existence of a future-o-scope to inerrantly reveal what the future holds. This hypothetical universe is, practically speaking, a block universe, where everything that happens is fixed, and any inhabitants who experience time merely experience a playback, and the future-o-scope would merely give glimpses into other time slices of this block universe. This is what it means for there to be a device that can inerrantly reveal the future: It being inerrant means the device cannot err. Such a universe can therefore absolutely not evolve to bring about events in a fashion that conflicts with the device’s revelations. It is essentially fatalistic. Suggesting that an inerrant future-o-scope is not in conflict with libertarian free will is suggesting that nothing being up for anyone’s choosing is somehow not in conflict with some things being up for someone’s choosing. I do not know how to address a stance like that.