What's the best paint stripper for a few decades' worth of paint on a
steel door?

The top layer or two peel off the underlying layer in sheets once I get
a finger nail under them, but Bix Original Stripper doesn't seem to be
doing a lot (and it seems to me that it smells different from the
identically labeled stuff I've used before). I also tried some
orange-colored citrus-based stuff that was on clearance, but it doesn't
do a whole lot of good either.

Perce