I’m struggling with the same issue here
i7 8700K
64GB DDR4
RTX 3080
1440p gsync monitor
Pre-update used to get 25 - 40 FPS regularly at ultra settings. Post update dipped to sub-10 (5-9 FPS). After much distressed troubleshooting, a clean reinstall of Nvidia drivers seemed to bring FPS back to pre-update levels.
The larger question for me is the sub-par frame rates anyhow - others with inferior tech specs are claiming much better frame rates.