Outlook groups - how to send emails from Groups

In order to add the ability to send from the group mailbox, this must be done in the Exchange Admin Center. You add delegates to the mailbox, just like with a Shared Mailbox. Unfortunately, that is not dynamic, and you cannot set the membership group as a delegate so that as members are added, they are automatically granted the ability 'send as' the mailbox.
https://learn.microsoft.com/en-us/microsoft-365/solutions/allow-members-to-send-as-or-send-on-behalf-of-group?view=o365-worldwide&source=docs

-Chris