It’s way more story-driven. While the main plot is same (Escape the planet), the storyline is much different.
You know the story of Subnautica, I’m sure. In Debris, you are a member of a filming crew. Some stuff happens and you get stuck under a frozen ocean. Your crew is lost, and the only way to survive is to reach to the surface. Of course, there’s a catch. Power is limited, and there are creatures much, much bigger than the Sea Emperor lurking around.