Since the latest update the game crashes at the main menu and also stutters constantly, as if the req has been raised significantly, I don`t know at the current state I cannot longer run the game properly, although in early access and the day of its release, everything was fine.
Anyone else got the same problem?

I've had a few stutters during switching camera's in cut-scenes.
But no other problems at all (yet).

The latest updates, which are not on GOG yet, supposedly improve performance among other crucial things.

Try running in forced DX9 mode instead of the now default DX11.
I've had performance issues as well. For one, they increased the amount of detail since back then, and on top of that they switched to DX11. Both of these caused a noticable performance drop for me, to unsteady ~15 FPS, compared to the perfectly playable sandbox days. I lowered all the settings, other than textures, and run the game in DX9 instead, giving me at least 20 to 35 FPS, usually around 25.

Switching to DX9 is done with a command on launch:
Either you edit the .INFO file (careful with typos though) in the game directory to make Galaxy start it in DX9...
[ ... ]
"name": "The Long Dark",
"path": "tld.exe",
"arguments": "-force-d3d9",
"type": "FileTask"
[ ... ]

Or, if you don't want to use Galaxy, just change the shortcut to the game like so:
"C:\Program Files (x86)\The Long Dark\tld.exe" -force-d3d9

If it won't start because of the settings being too high, you can get to the settings menu by overriding the saved settings with another switch: "-graphics-low"

If you're running into other problems after that, you might wanna try adding "-popupwindow" to the arguments, too. This enables borderless fullscreen mode, mainly for when the game crashes with "couldn't change resolution" error. If it doesn't, you should be fine, though.

All of this is taken from here:
https://steamcommunity.com/app/305620/discussions/4/487876568242614406/