Premise

So basically, the start of this universe is kicked off by Earth's ultimate demise. This can be whatever kind of cataclysmic event you wish for, just make sure that Earth is uninhabitable for a REALLY long time.

However, the leaders of Earth had somehow knew a disaster would befall Earth, so they advanced their space-faring technologies, some supplementary technologies were lost however, such as serums that could slow/halt aging after a long process.

Enough with that though, while space travel is possible, even interstellar for some countries, not every country had the same agenda. Some partnered to progress the Nomad Initiative, a group that travels the stars in search of discovery, scientific advancement, and the overall thrill of being among the cosmos. Note: they are generally a peaceful people, rarely engaging in fights, pursuing more diplomatic approaches.

Other countries pushed the Empire Project. This group that have moved past the home system, similar to the Nomads, but they instead create new Kingdoms and Empires that span many systems. These are chaotic and aggressive people, looking down upon the Nomads and Solists.

Then there is the hopeful Solist faction. They are quite religious and believe Earth will move past its current state and become an environmental utopia once again, or at the very least inhabitable. They refuse the help of the nomadic tribes, relying on their own prowess and resources in the solar system.

One of the final groups are the pessimistic Immolators, they are the outcasts that not even the Empirists would house, or the crazies that refused to leave Earth. They are thought to be completely killed off, and they might be, it depends on how you wish to take this story.

The final group is the Believing Colonists. They are a sub group of the Nomads, as they have broken from their tribe and settled in a star system they have deemed their new home, pursuing culture and the passion that the colonists and builders of Old Earth once had.

(Considered a sub group of Nomads as the Nomads transport them, few stay with the colonists)