public CIMRenderer Renderer {get; set;}

//Note: Run within QueuedTask.Run
//Get the Layer Document from the lyrx file
var lyrDocFromLyrxFile = new LayerDocument(layerFile);
var cimLyrDoc = lyrDocFromLyrxFile.GetCIMLayerDocument();

//Get the renderer from the layer file
var rendererFromLayerFile = ((CIMFeatureLayer)cimLyrDoc.LayerDefinitions[0]).Renderer as CIMUniqueValueRenderer;

//Apply the renderer to the feature layer
//Note: If working with a raster layer, use the SetColorizer method.
featureLayer?.SetRenderer(rendererFromLayerFile);