The absolute BEST way to "audit" the RNG's is to have a database of EVERY hand played on the site, it should be anonymized data of course, remove all player name data... but just continuously perform rigorous statistical analysis of that data stream in real time, nonstop, 24/7/365
Of course, no site is doing this, nor has anyone proposed they do it. It's not in the best interest of any site to perform this testing on their RNG (it is in the players best interest of course, but not the sites). They have no incentive to ensure their RNG is random, no player is going to stop playing on a site because they haven't rigorously tested the RNG, we're suckers and saps for the most part. We'll believe anything we're told, just look at this past year of the "Plandemic" for proof of that statement.
For those who know the AP/UB story of the "Potripper" superuser account... it seems foolish for us players to ever trust a
poker site 100%, they have no incentive to be honest or forthright with us, there is no consequence for cheating and there are huge financial incentives if they think they can get away with it without being caught... and with no RNG testing in real time, they could be getting away with anything and we'd never even realize it. Player beware, this is why I play with freeroll funds that I grind up and never play with "my own" money!!