On the advice of another thread, I used the name space UnityEngine.Rendering.Universal
and called the following on my scene’s main camera:
var cameraData = mainCamera.gameObject.GetComponent<UniversalAdditionalCameraData>();
cameraData.renderPostProcessing = false;
This successfully unchecks the Post-processing box for the camera in the inspector–however, this appears to be a purely cosmetic effect, as it does absolutely nothing as far as actually disabling post-processing effects in the scene. Surely there is some way to accomplish this?