Authority doesn't really work on the net. The information will be discarded anyway if people just want to.

When they use Breitbart as a 3rd party fact checker how can we trust them?

3rd party fact checkers themselves are highly biased. If you think reuters is neutral, then you really don't understand the "news" business. The "news" business isn't in the business of news. It's in the influence business. The founder of reuters started off peddling radical revolutionary propaganda.

Paul Julius Reuter worked at a book-publishing firm in Berlin and was involved in distributing radical pamphlets at the beginning of the Revolutions in 1848.

https://en.wikipedia.org/wiki/Reuters#History

Besides, the problematic part with "news" involve "non-factual" news but rather political "news". Whether globalism is good or bad. What, if anything, to do about climate change. Nonsense like veganism, etc. There, by nature, can't be fact-checked because it is a value/contextual judgment rather than a factual one. Capitalism vs communism, nationalism vs globalism, immigration vs nativism, alt-right vs alt-left, traditional media vs social media, etc.