Strict determinism as I understand it posits that all of our actions are predetermined by (a) the laws of nature/physics and (b) past events. Basically, everything can be traced like an incredibly intricate but ultimately predictable domino chain from the big bang. I think a physicist who believed this once made a falous claim that if you were omniscient about the laws of physics and one atom, you could predict the entire future of everything in the entire universe based on that information.

Keeping this strictly scientific and non-religious, as your post dictates—quantum mechanics can throw a wrench into the “laws of nature” part of this idea. Determinism depends on the idea that the laws of nature/physics are completely and utterly fixed. You can’t predict where a given domino will be unless the laws that the determine how each domino falls do not change. If the laws glitched and one domino randomly fell in the opposite direction, the chain would be disturbed. Some interpretations of quantum mechanics suggest that the laws of physics are less fixed than we would like to believe, and that the universe we live in is much more one of probabilities. This means there is a randomness factor. It is a very very very small one. That’s why we don’t see people accidentally walk through walls every day, or in a lifetime, or over the course of a hundred million lifetimes. But the possibility exists, according to some interpretations of QM, for “random”/“miraculous”/“law-breaking” events to occur. This means the laws are not entirely fixed, meaning everything in the universe might not be dependent on laws and history, as determinism states, meaning determinism may be wrong.

That’s my understanding of one scientific counterargument to determinism.