Not sure I can help here - while we did find a few online resources that were useful, our kids are in their twenties now so I can't remember much of what we came up with ten or so years ago. A lot was what might be considered "HN common sense" or pedantry. Looking at a site, article and author and deconstructing their bona fides, playing spot the flawed reasoning, appeal to authority or whatever.

And an awful lot of encouragement to question their beliefs, assumptions, and the spin of any particular article, or the motivations and intent, and change their own perspective at will. In short trying to encourage them to stay in the awkward squad who are constantly questioning...