I think art galleries are the wrong venue for black artists. They need to go where black people are actually buying art, instead of the venues were white people go to buy art.
From the art collectors I know of who are black, they prefer more direct to consumer approaches When purchasing paintings or sculptures. They will curate who they purchase art from based on referrals or finding your page directly on the internet.
I think your highest chance of getting sales is marketing to black people who appreciate your art for what it is and appreciate you for the type of artist you are. Now if you were trying to enter the galleries for the sake of reaching white audiences, That's a different story. I think it's a structural issue Because black people own so little of the underlying infrastructure. There are very few black agents to get work into galleries, very few gallery owners who are black, very few donors to museums are black, and very few museum curators are black. Until these structural issues are solved you're going to have a very difficult time accessing that white market or raising black representation beyond 1%