Black migration north into industrial cities helped start unions to keep out that “cheap southern labor”. Northern cities were racist, but they were more modern, cities and weren’t the deep south.
There was a shoot out with a black doctor in Detroit, IIRC.
I'm not saying that life for African-Americans was ever a bed of roses, with no thorns, anywhere here.
I'm only contending that pro-Confederate claims of blacks historically being treated better in the South than the North are not substantiated by any empirical data I know of.
Yes, in recent years many Northerners, doubtless including blacks, have migrated south for the warmer winter weather and... well, Southern hospitality.
But, to my knowledge that never happened in the past.