scene background color not sampled to material shader

[outer canyon]

Tried with a basic material and it works

        const debugQuad = new THREE.Mesh(
            new THREE.PlaneGeometry(2, 2),  
            new THREE.MeshBasicMaterial({ map: this.screenRT.texture })
        );
        debugQuad.frustumCulled = false;  
        scene.add(debugQuad);

[night granite]

If you can make a sandbox it’ll be easier to debug