Three.js outlinePass add-on not working when implemented with R3F

[MiguelG97]

I'm having a hard time using the R3F -postprocessing library so I decided to use raw threejs classes:
By diving into the R3F extending third party library tutorials I managed to setup the renderPass and the outlinePass with typescript https://docs.pmnd.rs/react-three-fiber/tutorials/typescript

The code is in the following sandbox:
https://codesandbox.io/p/sandbox/r3f-outlinepass-vdvhm8

Now I wish to add a mesh to the scene and trigger the outlinePass effect on it.
I tried pushing the mesh to the selectedObjects but the Outline is not working:

    const outlinePass = ViewerModel.effectComposer!
      .passes[1] as unknown as OutlinePass;
    outlinePass.selectedObjects = [];
    outlinePass.selectedObjects.push(mesh);