There's never going to be any conclusive evidence of the source of covid, and anyone claiming they have certainty (who wasn't a witness to a lab leak) is simply lying to you. What they're doing is going along with everyone else worth listening to, who find the coincidence that we were funding banned research on coronaviruses in a lab a few feet away from the origin of the outbreak unlikely. They also find tales of non-lab origin both speculative and vague, while stories of lab origin are only speculative.
It's so strange to demand so much more proof of lab origin than one does of non-lab origin. The obvious reasons for that demand are that millions died, and that everybody involved with that lab can easily be named. Also weird that this observation is covid-skeptic coded, when in reality the worse you think covid is, the greater the crime that a lab leak entails.