Hi @Jeanne Poirier,
Currently there is no such function to sync SharePoint file with local without onedrive. Here is a document for details
And if you are removed from your organization, the link will be disabled. You could only get the document with external sharing. You could refer to the document and the setting will need global admin permission
https://zcusa.951200.xyz/en-us/sharepoint/change-external-sharing-site
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