‘Race’ isn’t real in the sense that we use it. ‘Mongoloid’, ‘Negroid’, ‘Caucasoid’ are fictions of racism that don’t align with any evidence-based reality.
Sub-Saharan African populations are more genetically diverse than the rest of the planet combined; Aboriginal Australians are separated from by 60,000 years of descent, and Tamils and Melanesians all dark-skinned therefore would be identified as ‘black’ if living a society built on racism.
Racism isn’t grounded in reality, but it creates a reality people live in.
The construct of race is applied to people without their consent, and the idea of being ‘trans-racial‘ is therefore an absurd proposition to anyone who is not already viewed as a member of the supremacist class. A person categorized as a Jew or a Romani or a Slav was not able to say, ‘Actually, I’m German now’ in the Third Reich. That was not allowed to them. An ethnic German Christian might want to convert to Judaism, but if discrimination gets to much, that can be dropped for its inconvenience. If they’re lucky, of course, a light-skinned Romani might be able to move into the city and speak without accent—to ‘pass’. But if there are phenotypic difference someone can see or think they can see, even that’s not allowed.
A black person in the South can’t ‘feel’ their way to getting pulled over less or being treated with respect when standing on a sidewalk instead of being threatened with loitering. This is the main reason why someone who is perceived as white saying, ‘Deep in my soul, I’ve always felt more at home as an African-American’ is so ludicrous and offensive. This even affects people of ‘mixed’ heritage like Colin Kaepernick who essentially had to grow his hair out into an Afro to be taken seriously by other, more obviously & easily classified people. Historically, a person like Kaepernick might have been able to engage with society assumed to be of entirely European descent, which is an advantage not everyone had. On the other hand, Homer Plessy of Plessy v. Ferguson had only one black great-grandparent, so maybe not.
Being transgender is not the same because gender functions differently from race. It’s not just an external classification but how you’re supposed to feel about certain things.
Gender is largely a myth, too. I don’t think there’s anything real or set in stone about it. In some societies, women are supposed to be sex crazy; in others they’re not supposed to have a sex drive at all. Sometimes men are supposed to be the only ones capable of experiencing true emotion; sometimes they’re supposed to be stoic and a woman’s womb make her hysterical. Sometimes there are third genders or more.
There is some basic sexual dimorphism in humans, and people generally are born with some relation to that. But the person you experience yourself to be based on your own genes and how those genes express themselves in your environment may align strangely with what others expect you to be and do, which means you feel more comfortable as another gender than others have assigned you, or both of them, or neither.
The best explanation of epigenetics I’ve found is that it’s like making a cake: it’s not just the ingredients or temperature but the specific conditions involved in baking it at every step. If you take the same physical material but combine it under different conditions, the results can be vastly different. An individual has no control over their material or conditions, at least until they reach a certain age. By then, a lot of traits already have been ‘baked in’ to who they are as a person, and there’s no working backward to undo or change anything.
Gender is a spectrum of traits we’re all expected to have to some degree but in greater or lesser concentration depending on how we’re perceived and which society is doing the perceiving. Thus saying, ‘My idea of self is more comfortable and akin to this classification over here’ is no more or less ridiculous for being a cis, trans, or non-binary classification. Americans used to put little girls in blue & boys in pink, and both wore dresses; Scots men wear skirts and many indigenous cultures don’t expect women to wear shirts. There’s no immutable natural law about any of this.
To my mind, the identity of gender, and therefore being transgender, is a sort of temporary phenomenon—not because it’s not legitimate or sincerely felt or even a measurable quality but because once you get to a society where an idea of gender is no longer rigid or regarded as something immutable, people won’t experience gender dysphoria. The religious beliefs of a person used to be intrinsic to their idea of self, and still are very important to many people. But you rarely see someone who primarily defines their self as Calvinist versus a Lutheran, or a Roman Catholic versus an Orthodox believer. Some don’t bother with a religious definition at all anymore.
Coming out or transitioning is a working solution currently for those who do have that experience, but ultimately if gender identity isn’t oppressive, the idea of having anything to transition from or to will be irrelevant.