The problem is how to get the average reader of Tennessee Star to do a fact check on their "local newspaper". I think we need to pressure tech companies into taking responsibility. YouTube is experimenting with fact checking in India these days. Facebook and Google Search need to do the same. Maybe even web browsers should show warnings when visiting known misinformation sites. Tech companies got us into this mess, they should be held responsible and help us out of it.
Yeah, browser plug-ins are a great idea, but my grandma's on internet explorer, and I don't even know if she goes anywhere except Facebook, ya know? For the life of me, I can't figure out how to solve the problem of the 65+ demographic.
With how most browsers are engineered, I don't think there's a need for putting it into the workings of a browser. It's a perfect use-case for browser extensions or releasing something similar to Firefox ESR with a bundle of pre-installed and pre-configured extensions (it's essentially the idea behind the TOR Browser, at least its early releases). Plus consider all the outcry resulting from making it opt-out. Libel/slander, "who watches the watchers", accusations of censorship, genuine false-positives, media outlets using the tool against competitors, and who knows what kind of legal implications. Those always follow even in much more benign changes when it comes to content flagging.