I am speaking as a layman. I'm not a lawyer - just a nerd. Still, defamation cases are in the news.
My impression is that most of the potential defamation suits which are expected to come from Kyle Rittenhouse will go nowhere. Yes, if you're still calling Rittenhouse a murderer at this point, you're retarded; but, it's not illegal nor malicious to be retarded. I'll defend to the death your right to be retarded.
That said, I think he might have a serious case against The Young Turks. TYT has managed to tell lies about him, roll the lies back, and then start spouting the same lies that they had previously retracted. That shows actual malice. At this point, at the very least, TYT seems to have plausibly checked all the boxes for defamation. That and MSNBC.
Rittenhouse is probably not gonna get much from any lawsuit; but, I hope he does get something out of these liars.