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An event in a user's calendar, or the default calendar of a Microsoft 365 group, is an Outlook resource. The Event Graph API will list only the available properties in its response. You can check the properties of the event resource here: https://learn.microsoft.com/en-us/graph/api/resources/event?view=graph-rest-beta#properties
A channel is associated with the Teams resource and does not have a direct relationship with the event resource in the current Graph API.
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