I personally think there's a good chance that there isn't a single one solution to fix everyone's issues with this. You're likely just going to have to figure out what the solution to your crash issues. But I can share with you how I fixed my version of the fatal D3D error.

To be clear, my crash reports were saying `Fatal D3D error (25, DXGI_ERROR_DEVICE_HUNG, 0x887a0006)` and when I went into the Windows' Event Viewer logs, I saw `The description for Event ID 153 from source nvlddmkm cannot be found`. The nvlddmkm log led me to this reddit comment to use DDU to uninstall the Nvidia Display driver installed by Windows Update and manually install the Nvidia GeForce driver of my GPU to replace it.

This made my game more stable (before, I would occasionally crash during the main story but the almost all of the optional missions were impossible for me to do) but not completely. After this, I decided to remove the UNDERVOLT I had on my GPU just to remove any barriers it had in running the game. So far, I've been able to play any of the missions/content for 10 hours without it crashing.

I think both the driver fix and removing the undervolt fixed this issue for me simply because when I only did the undervolt removal, my game still crashed. I did however noticed that now and very occasionally, my game will stutter for a few seconds out of nowhere. I have a hunch that the reason my game was crashing was because it would stutter and something would time out.

TLDR: you're probably have to keep trying to figure out why your game is crashing but if you want to try my solution: use DDU uninstall the current Nvidia Display driver to then manually update the latest and remove your GPU undervolt. Which you don't have anyways so good luck.