Hello I guest you are not super admin. So, you can't use migrate service from 3rd party such as cloudm. If you are super admin you can contract to cloudm directly. They have a migration tool thay can migrate google workspace to google workspace also ...

There is a 3rd party opensource and free. It named GAM. It is a command line application and useful for google workspace admin.You can start at https://github.com/jay0lee/GAM/wikiExample command to set user signature.https://github.com/jay0lee/GAM/wi...