Reference:
https://learn.microsoft.com/en-us/purview/endpoint-dlp-getting-started
https://learn.microsoft.com/en-us/purview/device-onboarding-overview

The rule with priority 0 is processed first.
Reference:
https://docs.microsoft.com/en-us/microsoft-365/compliance/dlp-policy-reference

Explanation:
Reference:
https://docs.microsoft.com/en-us/office365/securitycompliance/labels

Correct:
* OneDrive accounts
Incorrect:
* Microsoft Defender for Cloud Apps
* Microsoft Entra security groups
* on-premises repositories
* Teams channel messages
* Teams chats
Note:
A Microsoft 365 auto-labeling policy can be applied to Exchange mailboxes, SharePoint sites, and OneDrive accounts. It can also be applied to content within Teams and other Microsoft 365 Groups, as well as Azure services like Azure SQL and Azure Cosmos DB.
Exchange Online: Applies to emails in transit.
SharePoint: Applies to documents stored at rest in SharePoint sites.
OneDrive: Applies to documents stored at rest in OneDrive accounts.
Teams: Applies to documents stored in the SharePoint sites associated with a Team.
Azure and other data sources: Can be extended to apply to data stored in services like Azure SQL, Azure Cosmos DB, and more.
Reference:
https://learn.microsoft.com/en-us/purview/apply-sensitivity-label-automatically

To prevent the contents of files stored in Channel1 from being included in Microsoft 365 Copilot responses and ensure unauthorized users cannot access them, you should use Microsoft Purview Sensitivity Labels.
Sensitivity labels allow you to classify, protect, and restrict access to sensitive files. You can configure label-based encryption and access control policies to ensure that only authorized users can access or interact with the files in Channel1. Microsoft 365 Copilot respects sensitivity labels, meaning if a file is labeled with restricted permissions, Copilot will not use it in generated responses for unauthorized users.