Are you a HubSpot Professional or Enterprise customer who tracks or hosts (Enterprise only) multiple domains or brands in the same portal? Then this is for you!
This post explains in detail how you can use the HubSpot Reporting Add-on to create sources reports (inclusive all the drill down reports) for specific domains, brands, products, subdomains and even subdirectories. Please note that this is a (very good) workaround, however as with all workarounds there are some limitations.