Plantation" = labor camp;
slave-owner = enslaver;
Union troops = US troops.
I’d keep the original terms for all of these concepts. A plantation is an large-scale farm in the American South, from the Antebellum (which is itself a southern-oriented term) or Plantation Era, white owned, with slaves. The term “labor camp” is a sanitized, low-information word, requiring phrases and clauses to provide the same meaning as “Plantation”.
Slave-owner is a fine term. Those plantations didn’t enslave those Africans: it was often Arabs and other Africans satisfying markets for human flesh that was vastly enlarged by European demand for slaves. When slaves were no longer available, those Plantations didn’t engage in enslavement themselves. Enslavers is inaccurate and clumsy.
Finally, Union troops: from Wikipedia “During the American Civil War, the Union was the term used to refer to the United States of America, and specifically to the national government and the 20 free states and five border slave states which supported it.” It was the Union Army, raised for the purpose of fighting our civil war. That’s what they called it.
This renaming is purely political, in the wake of the recent victory over the Confederate flag. Far better to keep these more descriptive terms than to attempt to perform “language cleansing.” It’s an overreach with no justification.