Nobody has found or even so much as proposed a very good one. There's a bare handful of reactions that can tend to amplify chirality, but most uncontrolled chemistry (including things like Miller-Urey) produce a biologically-useless random high-entropy mix, and it is fairly unclear that these handful of reactions, which aren't even necessarily obviously useful ones and require some fairly special conditions, could possibly overwhelm the entropy of all the other reactions blasting out random combinations of things.

AFAIK there isn't even a known way to start with "normal chemicals" and produce highly-chiral reactions reliably in the lab. We get all our chiral molecules by extracting them from biology.

The question is "how?" though. The chirality filter on Earth is basically Earth-life: it almost ubiquitously creates left-handed amino acids. But all known chemical ways of doing this produce racemic mixtures of both types.

If we found say, a high pressure synthesis method which was heavily biased chirally, then that would be good evidence but none has been discovered.

Is there any evidence of one or such a theory?