Documentation for configuring Mirror Gateway is available in your CloudSOC tenant. Navigate to Knowledge Base > Gateway to find the "Configuring Mirror Gateway for Office 365 with Okta" and "Configuring Mirror Gateway for Office 365 with AD FS" tech notes. Below is a support article guide to the tenant knowledge base.
I am honestly not sure what the road map looks like to extend functionality to additional services.
https://support.symantec.com/en_US/article.DOC11541.html