In the article above, the author addresses supposed myths and claims newspaper and cardboard are more toxic and dangerous than most people think. Are what he/she says true or just hype?

OH Brother!
Paper hasn't been bleached with chlorine bleach for around 30 years. These days pulp mills use Oxygen bleach, same stuff as color safe laundry bleach.

The only way for there to be dioxins in newspaper nowadays is if they are still recycling old newspaper from back when they did bleach with chlorine. Or its imported from a country that still uses chlorine. Paper is heavy and expensive to transport. Newspaper is the cheapest ( least processed ) grade of paper. Its cheaper to make our own.

As for the rest of his tirade i snorted my coffee when he claimed that newspaper has no nutritional value for plants.
However, it is true that paper has no nutritional value for PEOPLE.

in addition, he's correct in saying paper/cardboard [carbon] have no nutritional value for plants, their value is as fuel for microbes ["carbohydrates"], which is the part he appears to not understand - soil microbiology

there's nothing "toxic" about paper or cardboard, they're just carbon rich materials quite the same as sawdust or dry brown leaves

Bill