I agree it's a great time to start a campaign. And if a new book or movie or comic comes out, and contradicts what a campaign has laid out, who cares?
There are definitely going to be some First Order supporters, maybe even First Order military assets left out of the destruction on Exegol, that try to impose "order" on as much space as they can claim.
Also, might be worth exploring the planets/sectors in the Unknown Region that supported and helped grow the First Order.
What happens to all the Force Users alluded to in TLJ? If Rey tries to set up a new Jedi order, that brings one set of advantages and challenges. If she pulls a Luke and nopes out of training new Jedi, then perhaps a different set of challenges.
What if there's another powerful Force User awakened by the events of the sequel trilogy that doesn't, for whatever reason, get trained by Rey? Could that person try to pull the galaxy together under their banner?
What about a charismatic leader that convinces a following that Force Users are essentially responsible for the past 70+ years of galactic warfare, and that Jedi, Sith, et.al. should be shunned and kept out of any kind of roles of authority?
Lots of fun possibilities to explore!