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Teams Direct Connect allows for cross-tenant shared channels (the team and channel will appear in your own tenant), but this requires changes to allow cross-tenant delegation (see above link).
Teams Direct Connect
This option is not yet available. Please contact your customer success manager if you’re interested in receiving early access to this feature.
During the pre-onboarding or onboarding process, you can provide Armor with the name and email address of a Teams administrator from your organization. Armor will create a cross-tenant shared channel and invite that user to join the shared channel.
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