I have reason to believe that if the outgoing administration claims to have reason to believe something but refuses to provide the evidence behind it, they are lying.
https://twitter.com/CT_Bergstrom/status/1350292056782954498
Here's a very serious, legitimate review of the possible origins of SARS-CoV-2: https://www.nature.com/articles/s41591-020-01205-5
Unfortunately, from my experience, most people are going to believe what they want to believe, based more on political affiliation more than anything else, and the empirical facts don't register too strongly.
And words like "empirical facts" and "independent review" in context of China, do not add much credibility.
If virus has natural origin, we should be able to find population of infected bats. Until then it is just another unproven theory.