
According to your original post, I understand that you want to grant Sites.FullControl.All permission for the registered Azure application and get admin consent in the tenant for this permission.
Here are steps:
1.Open the Microsoft Azure portal by using the account of a member of the Tenant Global Admins group.
2.Go to App registrations -> Select the registered Azure application -> Click "API permissions" in the left menu bar -> Add a permission -> SharePoint - Application permissions - Sites - Sites.FullControl.All -> Add permissions.
3.Click Grant admin consent for tenant.
4.Result.
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