Hi @Glenn Maxwell ,
You must to be a global administrator to add templates from lookbook.microsoft.com.
Reference:https://learn.microsoft.com/en-us/sharepoint/provision-sss-lookbook
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.