Short answer
HubSpot's KB: the custom report builder supports HubSpot forms, non-HubSpot forms, blog comment forms and legacy pop-ups, but not lead ads, scheduling pages or surveys. Form submissions and form analytics data sources can't be used in the same report.
1. In HubSpot
The relevant screen in my demo portal.

2. Worth knowing
For quick numbers, the forms list Analyze tab may be enough.