Hi @Stuart, Robyn
Each private channel has its own SharePoint site. The separate site is to ensure access to private channel files is restricted to only members of the private channel.
Only people with owner or member permissions in the channel will have access to the channel site. People in the parent team and admins won't have access unless they are also channel members.
If you want to add a private channel to OneDrive, you must be a member or owner of the channel.
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