I haven't seen anyone leading the planet
Nubia in recent history but even if that were the case you're welcome to write as Nubian Royalty but bear in mind that the Wookie suggests that they've historically held "elected" officials. Mostly corrupt, if memory serves haha. That shouldn't limit you though because SWRP is many, many years in the future and things could have easily changed. Just something to think about for backstory.
Even if someone was "currently" writing as Queen/King/Leader of a planet that doesn't mean you're barred from doing so. No one can tell you that you can or can't write on a certain planet, nor, RP a particular role
(unless it's a custom project). If we held every role in reserve for members that originally had them we'd stagnate.
(Ex. There have been many, many Queen's of Naboo or Hapes over the years. Sometimes, concurrently.)
It's kind of like Canon Artifacts. They're treated as copies because tracking who owns what is a nightmare, people go inactive, and it's not really fair. Chaos is a buffet as far as "Lore" goes aside from the
Timeline. Take what you want from it and leave the rest - Thank you for asking, though.