One thing I did not realize is that US researchers who conducted gain of function research tried to downplay and discredit the possibility of the virus originating from the wuhan lab. There was an anti-lab theory Lancet statement signed by scientists, and "Daszak had not only signed but organized the influential Lancet statement, with the intention of concealing his role and creating the impression of scientific unanimity."
Plus there's all the stuff about the miners shoveling bat poop for weeks and then dying of coronaviruses, and the Wuhan institute collecting and doing gain of function research on these similar-to-SARS samples. And then several of the lab's gain of function researchers became ill in late 2019. And there's the weird renaming of samples to hide the unmatched closeness of the mine samples and covid. This is just the absolute surface of the article. There's too much to list here
Edit: here's another amazement for the list: "Shi Zhengli herself had publicly acknowledged that, until the pandemic, all of her team’s coronavirus research — some involving live SARS-like viruses — had been conducted in less secure BSL-3 and even BSL-2 laboratories." And the article says "BSL-2 [is] roughly as secure as an American dentist’s office."
It also seems The Lancet letter doesn't actual address the question of lab leak. Only that it wasn't engineered. That was a pretty hot conspiracy theory at the time and one that remains far fetched. They didn't positively say it couldn't be a naturally occurring virus that leaked. I don't know enough to comment on gain of function leaves any hallmarks but I'm guessing it doesn't since it tries to replicate evolution.