Recently decided to give The Lord of the Rings War in the North a try, which unfortunately required buying a key off a third-party site for the PC version, as it's no longer available for sale. That said, I'd noticed as soon as I reached the second area, the performance absolutely tanked.
I've got an Intel Arc A770, so I'd wager it's more than likely a driver issue on Intel's side. That said, I found two solutions that seem to fix it.
Solution A (recommended): just use the latest DXVK (x86 binaries) from here. This appeared to fix the issue completely for me, though I can't be entirely sure if any other issues are introduced as I've not yet played through the entire game, but it seems more stable regardless.
Solution B: just turn off shadows. Under video settings, there's a toggle for shadows. You can turn them down to minimum, which will help, but I still saw dips in other areas, so it's probably just a good idea to turn them off altogether.
With that done, you'll hopefully have no issues with the game.