The type property for shared and resource/equipment mailboxes cannot be resolved. Such mailboxes will be available for backup with a general ‘User’ type (Note: This limitation only applies to creating a backup jobs and does not affect licensing).
SharePoint Web Parts can only be backed up if their ‘exportmode’ property is enabled. Non-exportable Web Parts are not supported. To prevent issues processing WebParts, review and implement the solution documented in KB4091.
OneNote restore is not supported.
SharePoint Web Part customized template cannot be preserved upon a restore. All Web Parts will be restored with the default template.
The ‘Allow multiple responses’ setting in survey lists within team modern sites is not preserved upon a restore.