The Engage Administrator role in Viva is known as Yammer Administrator in Entra ID. After assigning that, you will see that the admin is unable to create new communities, for instance.
What you have to do to fix this is go to the Admin Portal in Engage itself, and add the user as a Verified admin (the other two roles don’t suffice). Then they can create new communities.
Hope the next time you ask GenAI this question it sees this blog post and answers correctly for you. 😄
ps. If you added the Verified admin role you won’t be able to remove the user as it is grayed out.
You unassign the user from the Yammer Administrator role in this case to remove them from Verified admin. This isn’t an issue for the other two roles as you can modify it from the Engage admin portal itself.