[estaseuropano]

This is a complicated issue and requires a careful approach. I don't think any serious fact checkers simply declare non-mainstream views as false, rather they would highlight only issues where a clear scientific consensus exist. So you flag an article about masks being ineffective and quote a clear analysis, or you flag an article about the Chinese (or US) government purposefully spreading covid, but you don't flag an article discussing the evidence for and against origin theories. See e.g. also the EU imitative on Russian disinformation:

https://euvsdisinfo.eu/