Interesting that you dismiss any suggestions that it is anything that you are doing as 'throwing shade'. It doesn't have to mean that there's anything wrong with you, but why not explore the idea that maybe you are doing something that people are backing away from, rather than assuming that it's race-based? It could be something cultural, or maybe just something about the way you go about it, maybe you've ended up a bit defensive because of prior experiences, and that's coming across, making people feel a bit uncomfortable. Or any of a host of other traits that might just be making it harder.
I know that I have lots of things that make it harder for me to make friends; some of them I can work on, others less so. I wish I knew more about what some of them were. You've obviously got better skills that me if you've at least still got friends from school
I suppose, in a situation when meeting lots of strangers, I do tend to gravitate to people with shared cultural background, easier to start talking, find common ground, even just little things to begin chatting about, shared history. Although I don't mean it to, I suspect that probably does mean I subconsciously expect that is more likely to be the case with someone white. I am also from another continent, so it's not really specific details. But when I'm just meeting an individual, then I like discovering who they are and in finding points of commonality and interest, regardless of background.
It might also be to do with expectations of friendship. I haven't made really good friends since university, going through really big life changes with someone (who I still know, though don't see too often). Since then, I've met friends, who I know generally, sometimes do things with, see at activities, etc, but no-one that I'd really get close to in the same way. They have their own childhood/university friends, their families, their work colleagues, etc, and I am on tiny part of that. I might see them once at week at a class or a club. I think for a lot of people, adult friendships are like that. It's a different intensity to how it is at other stages. People need different types of people at different stages. I don't feel a sense of 'sisterhood' or 'connection' or anything, not in a really emotionally intense way like when i was younger. I think it's rare to really make new 'best friends' as an adult. So maybe you are also experiencing the difficulty in making friends that happens at different stages of life, and are attributing it primarily to skin colour, when it might be largely because of other factors.