Kingdoms in Exile is a collaborative fan-made expansion of the Halo universe. Completely dependent from Rozh's main project, the Infinityverse, it will tell its own tale, although some technologies may be shared to an extent. Keep in mind that you shouldn't just assume that rebels are taking over, either; groups like the United Rebel Front and other Insurrectionist cells are just as tattered by the old Covenant onslaught, if not worse off, as when compared to the UEG/UNSC.