After running a migration, you see the following error:
This object uses Guest Links, which are not supported and will not be converted. You must update the links manually at the destination.
Property 'Wiki Content': This object uses Guest Links, which are not supported and will not be converted. You must update the links manually at the destination.
This error occurs when you are migrating a web part or an item with metadata that uses a guest link.
Guest links use access tokens which let SharePoint know which file the URL is pointing to (you can think of them like unique IDs). Since a new token is generated in a migration, Sharegate is not able to locate the file the guest link is meant to access. Because of this, we cannot recreate the guest link at the destination.
You need to manually recreate the link at the destination of your migration, and update the value in the associated web part or item.
Note: The property Authoring Canvas Content refers to the content of a modern web part page for Office 365 or Sharepoint 2019. In this case, one or more web parts use a guest link, and must be updated manually.