While Star Wars: The Rise of Skywalker is often considered one of the weakest sequel films, it may have given a big hint as to what Rey’s next Star Wars movie will be about. In many ways, The Rise of Skywalker changed several canon facts about the Force and the afterlife. Characters who die in Star Wars are meant to enter the Netherworld of the Force, where they are at peace from the physical world. Only a select few Jedi who have special training are able to return to the physical world as Force ghosts. However, The Rise of Skywalker completely ignored and changed these rules.

https://screenrant.com/rise-skywalker-setup-next-star-wars-movie-netherworld-force-theory/