How to get "Following Sites" list for all users in SPO Sites

There is no way you would be able to get the list of users using PowerShell script, this is something closest what you can do get this.

http://sundarnarasiman.net/2014/03/26/how-to-get-count-and-list-of-documents-or-sites-followed-by-a-user-in-office-365-sharepoint-2013-site/

Please let me know if that works

Thanks,

Thuyavan