To migrate SharePoint Online sites from one tenant to another, you could use Mover or sync OneDrive for Business, but they cannot be used without network.
You could use the save site as a template to migrate SharePoint contents into HD.
(1)Download and open SharePoint Designer, open the site, click Site Options in the ribbon.
(2)Locate the property SaveSiteAsTemplateEnabled and modify the value to True.
(3)Go to "http://yourdomain.sharepoint.com/sites/site collection name/_layouts/savetmpl.aspx".
(4)Click include contents.
(5)Go to solutions under web designer galleries, click the site template, save as file into HD.
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