I'm not sure if this will help or hinder, but my understanding of science from my social science perspective is that whereas many things are accepted as 'fact' (the Earth is round and suchlike) the door is always left open for someone to do some sort of an experiment (following a rigorous scientific method including that it is replicable and the results are transparent) to show otherwise. So, if a flat Earther can prove themselves and the rest of the scientific community agree after they have verified the results then the paradigm changes (was it Popper who wrote about paradigms?).
So, if someone can actually show that there are 'more than two sexes' in a biological sense (i.e we have one that produced eggs, one sperm and one that does something else) and the scientific community agrees with them then there would be a paradigm shift.
As far as I know, there hasn't been. There has been some mumbling about gender, but this is not the same as biological sex.
About other things there is debate. I put 'AGP' into this category and of course, this is about behavioural science which is a little murkier than the physical sciences.
There is debate about whether AGP exists. There is debate about the DSM and what is included in it and what is not in each edition. This is because that area of science (in my view) is not always about experiment, but about observation and also about treatment.
There is capacity here for groups to lobby and to say that x treatment for y condition is harmful and anyway y isn't a condition that needs treatment.
This is rightly how 'fixing the gay' stopped.
But that area has now been intensely lobbied by those who believe in pink and blue brains and that men who dress in what are perceived to be women's clothes are 'the other gender' or 'another gender' and not getting sexually aroused from it. There is disagreement here form some men (Grayson Perry) who say they do as well as from women who have lived with men who have become aroused and ejaculated from wearing women's clothes. Roughly speaking, there is big money invested in lobbying against AGP being included and little money able to be invested to say that it should be.
But AGP remains a theory and an approach to understanding human behaviour still upheld by some in the scientific community. It hasn't been disproven. It is the site of debate, just as there was once debate between Darwin and others and there is currently debate about whether the universe is finite or infinite.
Thing is, it is a debate, it is still being waged and up for debate.
A problem is that research is conducted in universities who are pretty much corporatised these days. They won't encourage research in areas that might make them look bad. I won't use the word 'captured' because I don't think it is helpful or useful, but the playing field clearly is not even.
In my area, I'd love to do research with young people about subjects inc. how they came across trans issues, how young lesbian women understand their place in the world and so on (so, social science) - but I could not do this because my colleagues would shun me and I'd never get it published because the journals would be harassed by lobbyists to retract it (as has happened with some gender critical research). That does not create an environment for good science/research.
To Hibari - As for posting a list of articles that support your POV this is not good science either and it does not show an understanding of what science is about. I could easily post a list of articles that show the opposite - or send you to anatomy books that clearly talk about two sexes - the accepted orthodoxy as it happens. Without commentary and an explanation of why you think these are 'good science' and how they all fit together and refute the orthodox view, the list is meaningless. And, you have to accept that those who might disagree with you are equal partners in debate and not 'skeptics' - I don't think I have met a skeptic of science on FWR. We do have posters who are very invested in science because they are doctors, psychologists, biologists, engineers and physicists though - and we also have social scientists. So when we disagree please do respect that we disagree - please do not try to discredit us - I think you might find we are actually more experienced and qualified than you.