Of course, we can surmise a few things based on what we know. If it’s a Sith Trooper, then these soldiers must serve the Emperor. Palpatine is the only living Sith as far as we know, unless Kylo Ren has been his apprentice this whole time, or becomes one during Star Wars: The Rise of Skywalker. Or maybe Palpatine has another apprentice we’ll be meeting at some point in the new film.
Article source: https://www.cinemablend.com/news/2476307/star-wars-the-rise-of-skywalker-will-introduce-sith-troopers-to-the-franchise