First you don’t need vtkScalarToRGBA since that filter is to create a texture. You don’t need a texture. You just need to tell the mapper to show which ever array you want to look at.
Then you have a dataset not an vtkAlgorithm. A vtkAlgorithm will produce dynamically the underlying dataset. Since your stuff is static, you just need to do.
const polydata = ...;
mapper.setInputData(polydata);
actor.setMapper(mapper);
renderer.addActor(actor);