I know for a fact that buck breaking exists in a modern context.
Everytime a white owned establishment targets a black man to make an example of him as a show of force to other black men and women, that is buck breaking.
Firing black men without good reason, executing black men without due process, disgracing a black man's reputation without evidence. These are all examples of modern buck breaking designed to let everyone else know 'if it can happen to him, it can happen to you'.
The unfortunate part about it is when black people deny what's happening in front of them and pretend it's incidental and not institutional. The realistic black woman knows that the alpha black male has every intention on protecting and providing for her, either personally or professionally. But the disillusioned black woman doesn't realize that no other man of any other race has a vested interest in her survival. She really thinks non-black people are just going to get rid of black men and let black women skip into the sunset. No sweetheart, they hate you too. But your natural femininity is not an immediate threat to them.
Dr. Frances Cress-Welsing described it as fear of genetic annihilation but it's also fear of economic annihilation, fear of social annihilation, and the annihilation of every privilege their murderous, vile, treacherous ancestors afforded them. That is the end goal, threat extermination and self preservation.