This is an old one but recently has been brought up again by BBC News as part of a broader article discussing black British history.
https://www.bbc.co.uk/news/newsbeat-52939694
The article doesn't cite any sources, but if you're familiar with this debate you'll probably have seen The Guardian's article on the same subject from a few years ago:
https://www.theguardian.com/world/2009/mar/12/race-monarchy
Again, while he's not the first to suggest this, a lot of the modern discussion of this seems to have been generated by Mario de Valdes y Cocom, a historian of African diaspora. His two main points that Charlotte may have been African or of African descent are based on some of her portraits, and an ancestral link. The portraits as evidence seems the more shaky of the two, since they are based on subjective opinion of whether or not you think they show African features, and are stacked up against many other portraits which don't seem to hint at any heritage. The ancestral link is that one of Charlotte's ancestors 15 generations (and 500 years before her) was a lady called Madragana, mistress of King Afonso III of Portugal, and she may possibly have been Moorish... or she may possibly have been a local Iberian Christian who grew up in a Moorish kingdom.
I'd like to get a second opinion, but this seems very flimsy to me. The key ancestor in question is of unknown heritage, but even if we accept best case scenario for this hypothesis and assume Madragana was Moorish, at 15 generations back the degree of her genetic contribution to Charlotte is negligible. The new BBC article suggests that Madragana's son married into a family which may have had African heritage, thus adding to the contribution in Charlotte's genetic make up... but again, no sources are cited and I cannot actually find where this comes from.
It's worth noting that I've also seen other debates online try to address the distance in ancestry issue by suggesting that perhaps Madragana has nothing to do with it and Charlotte was in fact illegitimate, the product of an affair her mother may have had... but again, no evidence to back up this idea. Not to mention that notion can't account for the appearance of Charlotte's siblings and children, the lack of any whiff of scandal or absence of paternal rage or disownment, and as quoted in The Guardian article Desmond Shawe-Taylor noting that
... keep reading on reddit ➡
https://twitter.com/JoeBrunoWSOC9/status/1421114174978068482?s=19
