I tried removing these jagged shadows with the Shadow Terminator Offset slider in Blender 2.90 but they don't go away even if I crank it at 1, plus I'm getting horrible dark shadows all over the place by increasing this slider that much.
I used an 8K displacement texture applied to a subdivided plane with a Displace modifier. I then added a Subdivision Surface modifier with 5 levels of subdivision, totaling a whopping 10.5M vertices. I also tried Adaptive Subdivision but it didn't work as I left my PC rendering for 2 hours and it was still calculating...
How could I fix this issue?
Shadow Terminator @ 1.00