I don't know if there's many major outlets that are primarily investigative in the era of the 24/7 news cycle and the accompanying need to always have something fresh on the front page, but at least in the English-speaking world the various newspapers of record (think places like the New York Times or the The Guardian) still have a decent newsroom and publish original investigative pieces. In audio formats, NPR and the various constellations of associated organizations like the Center for Investigative Reporting do excellent work as well. There's also organizations like Bellingcat that specialize in deep-dive investigations using open-source intelligence, presented in a "just-the-facts" format without editorialization.

The Wikipedia article on news agencies is pretty good: "Although there are many news agencies around the world, three global news agencies, Agence France-Presse (AFP), the Associated Press (AP), and Reuters have offices in most countries of the world, cover all areas of media, and provide the majority of international news printed by the world's newspapers." Scroll down and you'll also find a list of some smaller news agencies, which tend to focus on local news.