To perform this guide correctly you need:

- Subnautica same versions installed
- Radmin VPN
- 10 minutes if time
- a friend
After you've installed Radmin VPN and created a network. Share your password with your friend and now you're almost like in LAN.
Launch Subnatica game and from the main menu go to Multiplayer:
Click Add a server, then name it and put the host's ID in the field.
Then choose a name and a color.
Then everybody else in the network should see created server.
I hope it was useful for you.