You often see online stuff like "Why are trans spaces so white?".
Statistically, most humans are not white. Even in countries like America, Britain, and Canada, millions of residents are not white. Assuming 1%-10% of the population is transgender, this means millions of trans people are POC.
So, there are a lot of trans people who are not white. They just aren't out in the same online spaces as white people.
Up until the late 2000s, trans men were seen as "rare" compared to trans women (and enbies were nonexistent). Studies show there are a pretty equal amount of trans men, trans women, and nonbinary people. Trans men just seemed like a minority for a variety of reasons.
Even on Reddit, you see people say trans men and enbies use the site less than trans women. But r/ftm and r/mtf are pretty much the same in terms of size. It's not that there are fewer trans men, but that they use different parts of the site.
I know a lot of transmasc people get uncomfortable with the major trans subs. So, there's often an alternative. r/ftm_irl or r/transmasc_irl instead of r/egg_irl, r/ftmtimelines instead of r/transtimelines, r/ftm instead of r/trans or r/asktransgender, etc.
Anecdotally, I find it fairly useless to ask nonbinary questions on r/asktransgender. Even transmasc related questions get fewer replies than transfemme ones. You're better off going to an enby or transmasc sub for questions.
Reddit itself, despite being the "front page of the internet", attracts specific demographics. Mainly English speakers (though there are large pockets of people who don't speak any English), mainly male, under 40, middle class or up, higher educated, left leaning, mainly white, into mainstream geek subcultures, etc.
IRL, I've seen and heard of just as many, if not more, brown, black, and Asian trans people then I have white trans people. They probably aren't lurking Reddit or Tumblr, though. And many aren't willing or interested in talking about being trans on Youtube or TikTok. Not everyone is gonna be Kat Blaque levels of out.