Perhaps ban them from receiving advertising revenue. Force them to go subscription only. Advertising revenue comes from clicks, not reads, we want people to actually read and contemplate. This is closer to what old-school newspapers did.
In theory, subscribers will leave outlets that lie to them for outlets that are more honest
and fact-based. Or, if I'm pessimistic, subscribers will give money to whoever does rage-bait the best...
Ban advertising supported information sources. If people want information they need to pay for it in order that the information serves them not the people with a budget for manipulation.
You could I suppose allow adverts where the information is strictly for entertainment, but given that was Fox News defence... I think it probably wouldn't work.
Even then it's probably hard to prove that insufficient checking was performed at publication time