https://medium.com/@yurideigin/lab-made-cov2-genealogy-throu...
There have been at least four other coronaviruses which crossed over from animals to humans before we had any real viral manipulation technology. So I suspect SARS-CoV-2 followed the same natural pattern. But that's still just a hypothesis, not proof.
This "I'm just asking, because it could theoretically be true" stuff is slowly getting tiresome.
https://en.wikipedia.org/wiki/Falsifiability
As a basic matter of epistemology we can almost never really prove a hypothesis. All we can do is agree that it fits the available data until something better comes along.
EDIT: Of course these proofs have a certain likelihood of being false, hence all the p-value chasing and confidence-level adjusting.