Don't be disingenuous, That is like me asking you for what was not found in discovery, or for proof that there was no collusion.
There was a private settlement and a non-disclosure agreement for all parties. So no one can provide any documentation of anything either way.
It is fair to conclude that if nothing was found in discovery to embarrass the NFL, then there would be no reason for the NFL to settle and instead have the grievance hearing go forward in order to make Kaep and his attorney's look like complete fools for pursuing a frivolous lawsuit.
That would have been a complete victory for the NFL and a humiliating defeat for Kaep if indeed there was absolutely no evidence of collusion. So it stands to reason the NFL paid Kaep off to silence him. If there was nothing to silence him about, then no reason to settle or have an NDA as there would be nothing to disclose.