Why does anyone think this is a solvable problem? Once there is sufficient notability only authoritarian censorship or jailing is going to work, to increasing degrees of force up to executions (and even then that won't silence supporters or there was any sort of group association). For people of lessor reputations, "canceling" might work, in the sense of public shaming or loss of income, but there is a ladder of force that is required.

If we want any sort of free society I don't think we _can_ stop fake news. We can only attempt to counter it with reason, debunking, and competitive rhetoric. We maybe can build tools that attempt to amplify debunking, build institutions trusted as neutral arbiters or that have other forms of credibility.