If you're looking to revert the Fallout 4 update, then you're one of the many PC players who have unfortunately discovered the long-awaited next-gen patch has disabled certain mods and made their current save unplayable. If you haven't turned off updates for the game and are now on version v1.10.980.0.0 then it's likely that some or all of the customizations you've added to the Wastelands are now broken in some way, which is a significant problem if your current save progress is tied to them. To help you get around this, here's what you need to know about the process to downgrade Fallout 4 to its pre-update state.
How to downgrade Fallout 4 to the pre-update version
If your version of Fallout 4 has automatically received the next-gen update then it is possible to downgrade it to the previous version, but unfortunately it isn't a simple process. To revert the Fallout 4 update you'll need to use the Steam console to manually download the previous updates, which are known as 'Depots', as well as the specific localization files for the language you are playing in. You'll also need to manually disable automatic updates for the game so your work here isn't undone, then systematically copy over the Depots you've downloaded. There are a few walkthroughs available to take you through this process, including via the Steam Community and Nexus Mods.
If everything has worked correctly, then you should see that Fallout 4 has reverted to version v1.10.163.0.1 in the corner of the start menu, which was the previous update from December 2019. If you're getting crashes soon after launch, and a message on that screen stating "Game update required to connect to Bethesda.net" then you have Creative Club mods that are causing a conflict. You can fix that by accessing your Fallout 4/Data folder under Steam common and deleting all files beginning with cc (ie Creative Club). That should resolve the issue, but if you're still having trouble then read the comments on those forums for further suggestions.
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