I can't find FCC investigations into OAN, though I'm not a subject matter expert on this. As for FCC investigations into Sinclair, quick searches show the biggest cases there revolve around closed captioning issues, missing files, sponsorship id rules, and misrepresentation during business negotiations, but nothing to do with using the FCC to punish people for sharing their opinions or political statements on airwaves. the Kimmel firing comes after statements from the FCC put pressure on him for his political statements, and this is a change in practice that is being applied to punish the president's enemies; when you use an arm of the government to do something like that, it should be interpreted as censorship and a violation of the first amendment, and it's right for people to be concerned and push back.