The "stormtrooper" villains on The Walking Dead returned in season 10, episode 20, in which viewers get a look into how the Commonwealth group operates. AMC's zombified horror-drama had an impromptu season 10 "finale" back in October - before it picked back up in February - due to production issues caused by COVID-19. The episode mostly focused on fighting walkers and the Whisperers, and at the very end, Eugene (Joshua McDermitt), Yumiko (Eleanor Matsuura), Ezekiel (Khary Payton), and the new character of Princess (Paola Lazaro) were on their way to meet Stephanie in West Virginia.
Eugene had been communicating with Stephanie via radio and the group showed up at the designated meeting place, a rail yard. Stephanie wasn't there, and everyone - especially Eugene - was disappointed. Ultimately, they decided to stay in the area and continue looking for "like-minded folks." Eugene insisted there were in fact other people in the area, and he was right. Floodlights suddenly flashed on, and they were surrounded by soldiers donning stormtrooper-esque uniforms, telling them to put their weapons down and put their hands in the air. The show has since continued after that episode, but episode 20 fleshes out what really happened to the four-person group afterward.
The Walking Dead season 10 episode "Splinter" offers some additional context. Mostly, it provides a lot of Princess' backstory/point of view, as well as offering a "splintering" of reality for her as her mental state deteriorates and she attempts to cope in the boxcar. It gave a little more of a glimpse at the oddly-dressed captors, but, overall, a lot is still unknown. According to the comics, they're from a community known as the Commonwealth. They're a group of interconnected towns that are around 50,000 people strong, are run by a governor, and have an army (which viewers have met) for protection and crime-fighting purposes. In the episode, as is both common and smart for self-preservation under post-apocalyptic circumstances, this army doesn't trust outsiders. They're skeptical of the newcomers, locking them in separate train cars in between interrogations.
And, when Princess is being questioned, they're clearly not playing around. The man talking to her is purposely depicted as ominous--he's the first "stormtrooper" to be shown without a helmet, but he's partially obscured by shadows. His questions themselves are fair for the circumstances, and his frustration with Princess' failure to explain herself is understandable. Of course, it's uncalled for when he smacks her across the face for "being a b****." Not counting this transgression, the episode does a lot to humanize these new (possible) villains. When Princess turns the tables on the young soldier during their scuffle in her boxcar, he comes across as sympathetic. It's hard not to feel bad for him, as he insists that the Commonwealth is a good community that merely wants to help, but needs to understand the motives and nature of those "seeking solace at their gates."
The Commonwealth starts to seem like it might not be such a villainous place after all, implying that maybe Eugene wasn't betrayed. But there's a lot more to the Commonwealth - a society built on a class system - whose arc in The Walking Dead comics is the last major story before the series concluded. However, with this Walking Dead episode's ending leaving things how it does, the Commonwealth soldiers certainly don't come across as "good guys" for now, but that doesn't mean they will be the ultimate villains for season 11 - depending on how the TV show adapts the comic.