These cannot be removed on Mosaic versions lower than 22.1. You'll need to upgrade to version 22.1.1 and above, where the functionality to delete SUGs is available.
The system function is: DELETE_SUG
This function enables a worker or worker role with the necessary permissions to delete service user groups. It’s disabled by default for all worker roles.
📌Note: To access the links, you'll need to log in to the Customer Success Portal.
To enable this function, you can visit the System Functions reference user guide for the steps.
If you'd like to upgrade, please submit an upgrade request Upgrade Requests