This is starting to feel like one of those online discussions that goes around in circles and doesn't accomplish very much at all.
Because you two are arguing two different things.
OK I've read all this and I'm still not seeing what these '17 types of brain' have to do with sex of the person in question.
These relate to the experience of gender.
Emphasis mine. Sex and Gender are two different concepts. Sex is a scientific definition, you have male, female, and various forms if intersex. Gender is a social construct that is typically defined by what's between your legs. But not always.
But if gender that you are can be determined unambiguously...that means what they're feeling is objectively different from reality, so by definition it's a delusion.
You're entitled to your opinion, there's mountains of research on the topic, you just don't like the conclusion.
and I've heard absolutely nothing that has persuaded me otherwise
That's a "you" problem.