Using the ON24 iPaaS partner platform Tibco Scribe, a feeder service can be setup to populate data extensions in Salesforce Marketing Cloud (SFMC). The ON24 service runs in batches and create a row of data using registrant data (first name, last name, email, company, etc.), and the update the row with attendee data (live minutes, archive minutes, engagement score, poll responses, survey responses, etc.).
Contact Support for assistance with the setup of Scribe.