Questions about Nitrox Multiplayer

Hi! I just finished playing Subnautica on my own and I want to start playing it with my boyfriend. I looked into Nitrox and had been trying to get it to work for a while, but when I try to start a server, it tells me that it's not compatible with the Living Large Update. Is there a way to somehow use Nitrox to create a new world without that update? And if so, how would it affect the gameplay? Thank you!