Hi @George Pinkasiewicz,
Thank you for posting in this community.
First, try to see if you can use the administrator account of tenant B to access https://admin.microsoft.com/Adminportal/Home#/homepage and
https://tenantB-admin.sharepoint.com/(Please change your tenant's real name.).
If you can, then you can export the list of tenant B users directly in M365 Admin Center > User > Active users.
Export the SharePoint sites created by tenant B directly in SharePoint Admin Center >Sites >Actives sites.
If you can't do it in the first step, then we need to do something a little more complicated.
In the Active users' page, you can filter users based on domain name before exporting.
But for SharePoint sites, we don't have a way to distinguish which domain the site was created by a user for the time being, so we can only export them all and then manually distinguish them. Unfortunately, this can be complicated and time-consuming, but there is no better way.
As this forum is assigned to the support team of the relevant product by the question tag. We're responsible for the SharePoint product, so for the export of channel channels in Teams, we recommend that you re-ask questions in this forum and add the Teams tag so that the Teams team can discover your issue.
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