Every other theory requires involving many more unsupported hypotheses.
This would be obvious to the majority of the HN population in most cases, but the disinformation in this case is apparently quite effective.
How do we know that the virus (or a precursor) wasn't already circulating in China, and was simply detected in Wuhan because of the fact that there are experts in coronaviruses who reside there?
(Also I'm not entirely sure your statement about the gain of function research is correct. A Google search doesn't seem to provide any evidence one way or another.)
So, basically, you're saying that (many, we know how contagious covid 19 is) people got sick and put into hospital/died with a novel respiratory disease in another (or several other) chinese cities first. However, that was covered up or unnoticed _until_ it reached wuhan, and for some reason a researcher who works with coronaviruses at the lab saw a sick patient (at the hospital?), realized "that looks like a novel coronavirus" and decided to raise the alarm? Additionally, after that only Wuhan got shut down, while the other city or cities which should have had a raging epidemic by now still went unnoticed?
That's what I mean, these other theories to explain away what is the most staightforward explanation makes no sense, and invokes too many unlikely scenarios or coincidences.
Regarding gain-of-function, see [nature article from 2015](https://www.nature.com/news/engineered-bat-virus-stirs-debat...) questioning the safety of gain-of-function research, and the article that [triggered the reaction](https://www.nature.com/articles/nm.3985). Part of that research took place in the Wuhan lab.
(Then there are the conflicts of interest of the WHO investigator Peter Daszak, who is very quick to discredit any theory that the virus might have escaped from the lab...)
Again, this is a farce, and it would almost be funny if it weren't for all the dead and the generally shitty situation for most of the world at the moment.
What China and the CCP wants though is to have this debate centered around if it was lab produced or not. They can rely on western scientists to debunk the lab created hypothesis. That leaves their own theories about it originated in Italy as the standing theory for their own domestic consumption. And that avoids looking at their animal farming practices and keeps them from having to crack down on that whole economy, which would be highly disruptive.
And this keeps factory farming conveniently entirely off the radar as a cause of this pandemic. The next pandemic could easily be a virus that hops to humans from pigs or chickens in the USA. All the yelling both ways about lab origins is a very effective smokescreen to avoid doing anything to prevent a future pandemic. NOTHING will happen to prevent future pandemics over yelling about lab causes other than making some people in America very, very angry about China. What we should be doing is thinking about factory farming practices and reducing our diet of meat and animal products.
This would mean that we might have to admit that the insufferable vegans were right all along, and then change our own behavior -- so its much easier to just get super angry at China.
Bats — aside from the few blood-drinking bats which aren't implicated, and aren't they New-World species anyway — don't tend to interact much with other mammals or with birds. Without human intervention, there's not much opportunity for them to infect humans or any other animals. Carnivores (raptors, felines, to a lesser extent maybe even canines) do eat bats, but not commonly, and they're unlikely to spread disease further due to their lack of social behavior.
Neither bats nor pangolins are factory farmed (it seems some people have tried with pangolins, given their delicacy status, but they're not easy enough to raise in captivity to make it worthwhile). Bush meat and wet markets create other disease risks, but not the concentrated disease reservoir effect you're pointing out as a problem in factory farming, i.e. typically swine or fowl. There are many reasons to reduce factory farming (meat consumption per capita); disease risk is just one of them. Diseases in factory farms can be monitored, particularly these days with cheap DNA/RNA sequencing. Diseases from wild animals sold in wet markets... no surveillance... greater risk.
Given the bats are the most likely original source, and given that Wuhan lab scientists travelled and collected bat virus samples from where those species of bats actually live, the obvious most likely theory is that there was an accidental leak of a natural or derived virus from the WIV (or at least from WIV scientists on return from one of their trips if you cling to the theory that SARS-CoV-2 is of entirely natural origin).