Forum Discussion
Groups: Tenant to tenant migration
Groups use special forms of mailboxes that not all migration tools even reveal let alone access... That is my warning.
Just as an example, try using the Get-Mailbox cmdlet to list group mailboxes. They don't exist. You have to use Get-UnifiedGroup. But you can feed a group mailbox id into Get-MailboxStatistics... So it's inconsistent, hence the warning.
"the process of moving a unified group looks easy"...
That's some statement, especially because no OOTB tools are available to do the work.
The components you might have to deal with are as you listed, unless you use Teams, in which case you have chats etc. to move too. Planner and Teams share the same characteristics in that they store "their" data (as opposed to Files and plan comments) in data services outside EXO and SPO. You might be able to extract this data with the Microsoft Graph API.
SharePoint is easy enough because you are moving documents and files around - but be aware that metadata might be lost if you use file-level movement utilities. In other words, the devil is in the detail.
Extracting group conversations is, I think, possible with the Graph API too. Perhaps the AvePoint DocAve backup could help here as it now supports backup and restore of group conversations.
So getting at the data is possible. The issue might be stitching everything back together so that users see the same Groups as they had in the source and that all of the data belonging to those groups is in place and available, conversations are composed of the correct items, files are in the right libraries and have the right permissions (both for the group and any specific sharing), and so on.
Because no OOTB tools are available to do all of this, you are on your own. Good luck, fair sailing, and do let us know when you complete the task.