It appears the exterior cardboard junk that's used on my home's trim is
Masonite. I did some research and found that a class action suit against the
manufacturers of Masonite siding some years ago was successful. So far, my
research indicates the settlement does not cover trim; only whole walls.
Thus for now, I'm painting the trim I can but also would like to replace
much of it.

Are Home Depot and Lowe's suitable enough places to buy around 20 to 40 feet
of 4 inch wide (3/8 inch thick?), real wood, trim?

Anything to look out for?