Mesh collider without Rigidbodies

Hey guys,
I decided to use a mesh (without Rigidbody) in place of Unity’s built-in terrain, and I attempted to attach a meshCollider (non-convex). However, the collider doesn’t seem to work, and I can’t use convex as that would just ruin gameplay. Any thoughts, suggestions or alternate methods?

(Important: I’m using a asset called “Polybrush”!)

Select the object you want a mesh collider for.

In the toolbar at the top of the page in Unity, click on Component/Physics/Mesh Collider.

Find the original prefab object in the project window and its mesh (child) object. It has like an xray view with vertices

Drag the mesh object onto the mesh onto Mesh Collider (MESH)