I will be selling my M2P with Smart controller. Do I just need to sign out from the DJI GO 4 app in the controller or something extra need be done before handing over the drone to the new owner ?
Use dji assistant and reset drone and controller. I have the smart controller, don't know if you can reset the normal controller.
After that you should be signed out as well. I don't think there is more you can do.
Maybe there is a reset to factory settings button somewhere in the dji go app, don't know.