This isn't quite right. Firstly, Kimmel and his show were originally suspended, not outright terminated, according to statements by Disney, as reported by Politico. Further, as of now Kimmel has not filed a lawsuit that I can tell, though there has been speculation that he could file such a suit, as covered by Politico and Reuters.
Interestingly, Kimmel was involved in a recent lawsuit involving former Congressman George Santos--but it was a lawsuit against Kimmel, not by him. AP reported that "A copyright infringement lawsuit former Congressman George Santos filed against talk show host Jimmy Kimmel and ABC was properly dismissed by a lower court judge, an appeals court said Monday."
