Here's another grimderp campaign for you, OP.
The first intergalactic ship, the FALCON PUNCH, sets sail, heading for the nearby Andromeda galaxy, a hefty 2.5 million light years away. Thanks to photon sails, ionic blasters, etc etc, the ship is capable of traveling that distance in 2.5 million years on the nose. However, a mishap. Forty years into the voyage, transmissions stop, and not a peep is heard from the ship ever again...
ON THE SHIP
Okay, so, get this: there was a sabotage! The captain was killed, and the ship, carrying thousands of people, is divided. Tell you what, it wasn't a walk in the park. Since transmissions stopped, and with no link at all with Earth, morale drops, and people degenerate into tribes. Soon, with the ship's systems decaying, the tribes make Earth out to be a heaven, and the various people keep fighting.
You can introduce aliens if you want. Makes for a good story.