Re: TITANBP's report from yesterday, downgrading the game using Doomgrader as per his report allows you to play the game as per normal.

Set the game to update only when launched. Game needs to be started in Steam online mode first run after downgrading or you'll possibly get an error message telling you to do this if you do the first run in Steam offline mode (I was worried the game would try to reapply the May 15 update which borked things, but it didn't). Close game immediately after it launches, restart Steam in offline mode, start game.

To be on the safe side/to stop the game potentially updating, play game in Steam offline mode until Bethesda gives us a way to turn off anti-cheat if you only want to play single player (although it is relatively easy to recopy over the downgraded files to your Steam folders if the game does update).

Proton-5.8-GE-2-MF (earlier versions of Proton GE should also work fine).