Sabine Hossenfelder is an advocate for (although not necessarily very dogmatically) and has published papers on superdeterminism in quantum mechanics. She has a new blog post on the topic.
Some of the weirdest aspects of quantum mechanics are its seeming non-locality, particularly but not only when there is entanglement, and the fact that measurement changes how particles behave, with what constitutes measurement not defined in a very satisfactory manner. Superdeterminism is a theory that seeks to explain these weird aspects of quantum mechanics in a way that seems less werid.
Basically, superdeterminism is a hidden variables theory (with properties that escape Bell's Inequality like a lack of statistical independence) that argues that the non-local effects in quantum mechanics are really due to individual quantum mechanical particles having pre-determined non-linear properties that are measured when a measurement happens.
So, for example, the slit that a photon goes through in a two slit experiment is, in a superdeterminism framework, already determined when it is emitted.
Superdeterminists assert that the behavior of quanta is too mathematically chaotic to be measured or predicted otherwise, leaving us with average outcomes of chaotic processes that are functionally random from the point of view of an observer, even though they are actually deterministic at the level of the individual particle.
She also makes the important point that the colloquial understanding of free will is not consistent with the purely stochastic leading theory of quantum mechanics any more than it is with determinism, since we have no choice regarding how the pure randomness of quantum mechanics manifests itself.
The way that the term "free will" is used in quantum mechanics, which involves statistical independence, is a technical meaning that is a false friend and does not imply what "free will" means in colloquial discussion.
I am not convinced that superdeterminism is correct. And, she acknowledges that we lack the instrumentation to tell at this point, while bemoaning the scientific establishments failure to invest in what we would need to get closer to finding out.
But, her points on free will, and on the sloppy way that the Bell's Inequality is assumed to rule out fewer hidden variables theories than it does, are well taken.