Ultimately, the only way to resolve this question of sexuality is if Kit himself speaks openly, so until that there's no use bringing it up.
However, I've seen several comments in Insta ridiculing or being dismissive of Jonathan Bailey, the star of Bridgerton, because of his sexuality. Apparently, Bailey cannot be considered to have good chemistry with his female costar as he isn't straight. If people harbour such casual homophobic outlooks, I can't blame Kit or other actors from not being open about their sexuality.