So basically, the safest choice is to buy used furniture that left most of its formaldehyde at the previous owner since the industry is far from regulating it and there is no way to avoid it without living in a cave, but theses have radon gas aplenty.
Definitely, but solid wood isn’t affordable since the early 00’s. By that metric, IKEA is the only low formaldehyde content affordable fournitures since they are mostly honeycomb cardboard and covered in latex paint.