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One important thing to keep in mind is that the Disney+ audio description of the episode explicitly says, "Rows of similar compartments sprawl throughout the bay with an engineer in white coveralls tending to immobilized Dark Troopers contained within."
One take on Dark Troopers appeared in games like Star Wars: Battlefront and Star Wars, Dark Forces (among others). They resemble stormtroopers, but they're actually advanced combat droids cloaked in intense armor. Meanwhile, another version of Dark Troopers appeared in the Dark Empire series of comics, and are Force sensitive bad guys. The latter description fits in well with whatever Force-related hijinks the Empire was conducting in the lab on Nevarro.
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