: Your console will prompt you to download the update before launching the game while connected to the internet. Manual Downgrade to Update 84 (Advanced Users)
For a visual walkthrough on how to access and install specific legacy versions of the game, check out this guide: subnautica-update-84-installation-tutorial
If you are looking for Update 84 specifically to maintain compatibility with older mods or for speedrunning purposes, you can manually revert your game version using the Steam Console. : Your console will prompt you to download
: Press Win + R and type steam://open/console . subnautica-update-84-installation-tutorial