Added detailed description of limitation around archiving channel sites.

Author: considerITman

microsoft-365/archive/archive-overview.md

@@ -49,7 +49,11 @@ Administrators should notify the site owners and end users before a site is arch
 
 ## Limitations
 
-Publishing sites and a handful of legacy site template types are not available to archive with Microsoft 365 Archive. Teams channel sites are available for Archive only via PowerShell. 
+- Publishing sites, channel sites and a handful of legacy site template types are not available to archive with Microsoft 365 Archive. 
+- While sites associated with Teams with exclusively standard channels are supported for archiving, sites associated with Teams that include private or shared channels are only partially supported:
+    - SharePoint Admin Center: Archiving a site with channel sites is not possible. (Message: "The group connected site with channel sites associated can't be archived.")
+    - PowerShell & Graph API: Archiving a site with channel sites is not blocked.
+    Only the main site associated to the Team (and its standard channels) is archived; the private and shared channel sites remain active. Archiving the channel sites directly is not possible, as these sites use unsupported site templates.
 
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