KB439449: "Only USER objects can be added to subscriptions of type 'Email'" appears When trying to add a user group to an e-mail subscription in Command Manager

SYMPTOM:
When trying to add a user group to an e-mail subscription in Command Manager with the command:

ADD GROUP "<user group name>" TO SUBSCRIPTION "<email subscription name>" FOR PROJECT "<project name>";

It fails with the error "Only USER objects can be added to subscriptions of type "Email".
CAUSE:
E-mail subscriptions are editable only in Web and even there you cannot add a user group manually to such a subscription, as this feature is currently not supported. Hence, the above command returns an error in Command Manager.
ACTION:
Adding the above feature is not currently on the road map of Strategy. If you would like to know how to create subscription to multiple users, please refer to the Knowledge Base article https://community.strategy.com/article/KB36218-How-to-create-an-email-subscription-to-multiple-users-in.