Obviously you havent read what Luther himself wrote as opposed to what his fan club has made easily available and altered to suit their agenda.
You are correct. I could not find anything online showing what Luther said about the Deuterocanonical books. I know he had some things to say about James.
Anyone really interested can find these things on-line although I got hold of them through inter-library loan several years ago. Some of them were only translated into English in the sixties and seventies which is in and of itself pretty interesting. At the time I was still Lutheran and absolutely stunned by a lot of what he had to say and how much the popular myths about him differ from what he was really like.