Here is a workaround:
Publish your feature service with the symbology you want. Add the layer to your app using the GeodatabaseFeatureServiceTable and save the render json info as a json file from within your app using code such as:
app.folder.writeJsonFile(layer.name + ".json", layer.renderer.json)
Copy this json file to your app folder, then apply this json file to a renderer to use with your GeodatabaseFeatureTable. e.g.:
UniqueValueRenderer{
id: rendererFromJsonFile;
Component.onCompleted: {
rendererFromJsonFile.json = app.folder.readJsonFile("renderer.json" );
} }