The universe is not deterministic, but that’s completely irrelevant. The argument of free will does not rely on the lack of determinism of quantum mechanics.

If free will were to be true, you have to have the ability to have acted differently.

And how will you determine the existence or lack thereof, of the ability to act differently?
I’d say we very probably have this ability, since we often reacts differently in similar situations. Ergo by your own standard, your conclusion is wrong.