Superdeterminism looks like metaphysics to me. It seems an attempt to postulate a fundamental truth about the world, but without empirical foundation. Which experiment would falsify the superdeterminism hypothesis?
The one proposed in the paper: looking for time-dependent correlations in the measurements of quantum states that are prepared to be as identical as possible.
Nothing can falsify superdeterminism in general. If you proposed one specific model of that, that might be falsified.