The main protagonist is male but there are plenty of female protagonists as well.

As far as relating goes for most story lines you should be able to relate as much as one possibly could to a space opera.

Protagonist means "the main representative". So there can be only one protagonist.

By the way, it seems to me Expanse does not have a protagonist.

Actually, that's one of the good things about it: everyone's equal. Gender doesn't matter, only the character does. Just as it should be.

I prefer fiction where the women are defined purely in terms of love interests or other traditionally gender specific roles.