There is no such thing as Black supremacy. There never has been and there never will be.
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Black folks ain’t superior and any person spewing it has a personal motive. You should flee from them promptly. There is no way any Black person in America or Black people collectively can be Black supremacists.

Any person using the term is doing nothing more than deflecting from their own discomfort discussing race and is incapable or willing to deal with their adjacency to white supremacy.
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Black people cannot be racist, only prejudice (many people don’t know the difference between prejudice and supremacist)
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People using the term Black supremacists have an entirely different motive, and it’s keeping their White gate owners, employers, family members, and friends happy and comfortable. I’m not about to allow anyone (including Black folks) to use their privilege to scapegoat Black folks who recognize what white supremacy is going to them individually and to Black people collectively.

As Michael Harriot noted, Black supremacy isn’t a thing because Black people can never be supreme or superior. I also believe people misconstrue racism and white supremacy.
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Lastly, White and European people are the only people in the world who believe and act as if they are superior to all other races. The rest of us are just trying to either navigate or compete with white supremacy for seats at the table or scraps from the floor. This is a White man’s world. Black folks are just squirrels trying to gather a few nuts to survive the winter.
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Black supremacy is a made-up term coined by folks who either love/need their paychecks supplied to them by White people, are Black folks married to White folks who aren’t ready or willing to unpack their own ties to white supremacy, or biracial people torn between the Black/Brown parts of themselves and their other part — the White or White passing side.