What lines of evidence and arguments refute the notion that the gospels are nothing more than dismissible 'reports of reports of reports of reports'?

In a [previous question](https://christianity.stackexchange.com/q/101109/61679) addressing skeptical analogies aiming to cast doubt on the evidential worth of testimonies for extraordinary claims, I cited [this source](https://youtu.be/MEEEJ0SrC60?t=525) which I'd like to revisit here with a different focus: > *Stephen Meyer*: And then that there were reports that he had been, that he had appeared to many after being resurrected. So there's a whole ... > > *Joe Rogan*: Right, but there's reports of Bigfoot. > > *Paulogia*: Right again Joe, but at least for Bigfoot we have first-hand reports. For Jesus's resurrection all we have are **reports of reports**. At best. More likely, **reports of reports of reports of reports**. Bigfoot is in higher evidential standing. Suppose I pick up a modern Bible, say, a contemporary King James Version, and peruse the four gospels. How can I ascertain that I'm indeed delving into a reliable eyewitness account sourced directly from about 2000 years ago? How do I know I'm not just perusing a 'report of a report of a report of a report' that might have undergone significant manipulation and alteration over time due to tradition, vested interests pushing certain agendas, and so forth? What lines of evidence and arguments should persuade any rational, neutral, and open-minded individual into believing that the gospels we possess today genuinely preserve trustworthy eyewitness testimonies, and aren't merely dismissible as 'reports of reports of reports of reports' as Paulogia seems to suggest in the quote?