no, there is no out-of-the-box reporting on who adds events to their Outlook calendar from the Events webpart.
Use the Outlook Calendar API or Microsoft Graph API to write a script that queries all events in the tenant and tracks the organizer of each event.
Use a third-party tool that can track user activity in Outlook, including who adds events to their calendar.
Manually track this information by creating a spreadsheet where you track the date, time, and organizer of each event that is added to the Events webpart.
You could also use a third-party calendar sync tool, such as Zapier or Integromat, to track who adds events to their Outlook calendar from the Events webpart by using the tool's webhooks functionality.
If you are using a SharePoint site to host your Events webpart, you could use the SharePoint auditing feature to track who adds events to the webpart.
Please click Mark as Best Response & Like if my post helped you to solve your issue. This will help others to find the correct solution easily. It also closes the item.
If the post was useful in other ways, please consider giving it Like.