Very simple implementation of downloading onedrive files from one tenant and uploading to another, including fixing onenote notebooks.
The Connect function in connect.ps1 should be updated to how you want to connect to the tenants
.\download.ps1 2j32jn-my.sharepoint.com 2j32jn.onmicrosoft.com per,pattif
Downloads files for the users "per" and "pattif" from the onedrive creates a directory for each
Adds an file OneNotes.txt specifying which folders are really OneNote Notebooks
.\upload.ps1 xvb13-my.sharepoint.com xvb13.onmicrosoft.com per,pattif
Uploads files for the users "per" and "pattif" from the downloaded directories to onedrive
Marks the folders from OneNotes.txt as being OneNote Notebooks
To be able to actually read documents from users OneDrive and if you are connecting using a user account you will likely have to grant your user site collection admin permissions to the users onedrive. For that you can use the command
Set-PnPTenantSite -Identity $webUrl -Owners "<<your credentials>>"