Do we know who owns certain richlist addresses that are not related to an exchange? is there anyway we could find out?
Yes, through them voluntarily admitting that they own it and proving it through signing with a message that it's proof that they hold the funds.
But are they going to that for a show? Not really, they don't even care that they should be found out as the owner of it, and for sure that they better keep it private than publicly known that they hold such funds. It's for their protection and more of privacy.