Hi @RMD211,
As far as I am aware both in the interface and via the REST API you can only set one owner when creating the site initially. However, it should be possible to add more owners after it has been created.
There are different approaches. You could PowerShell, a Site Design, or you could for example add an additional owner to the related Office 365 Group.
Below is an example of that last approach.
You have to play a bit with the delay settings. It might take some time before your site has been created and the group can be found.
1. Add a Delay action. I used 16 minutes 😂
2. Add a Send an HTTP Request action. Use the List groups method of the Graph API. I am using a $filter parameter for the displayName
https://graph.microsoft.com/v1.0/groups/?$filter=displayName eq '@{variables('SiteName')}'
3. Use a Condition to check if can find the newly created group.
length(body('Send_an_HTTP_request_-_Find_Office_365_Group')['value'])
4. If Yes, Use another Send an HTTP request action with the Add owners method of the Graph API. In the URI the following expression is used to retrieve the Group Id:
body('Send_an_HTTP_request_-_Find_Office_365_Group')['value'][0]['id']
