In a pc game context I would try to make something like a no man's sky planet, but as you walk chunks of land in a radius around you get replaced with procedural new ones. something like a minecraft chunk loader that is relative to the player but wrapped around a sphere, and god forbid you actually want to have multiple players... Going into space can be more cursed but my favourite is: as you orbit the planet the active chunks scroll relative to your orbit with a speed relative to your distance; good fucking luck landing in the same place without insane math.