Trump sues Twitter in Southern Florida, as a part of a class that has been de-platformed. Count one is that the First Amendment has been violated, Count two seeks a declaration that Section 230 is unconstitutional, and an unspecified amount of monetary damages are sought. He sued Google and Facebook in separate actions.
Twitter’s Terms of Service has a choice of forum provision (California)
News coverage BBC, Axios, and C-Span.
Text of complaint in Trump v Twitter: trump v twitter complaint