
Hi @Hurley, T
Per my research, when you migrate linked files with SharePoint Migration tool, the links in documents won’t be changed as the document links of SharePoint Online will be different from the on-premise links or local files. Hence, the linked data is broken after you use SharePoint Migration Tool, and the Migration tool won’t change and replace with the new links in document.
You could send feedback to Microsoft SharePoint Feedback.
What's more, here is a similar case discussing about replacing the broken links with some third-party tools:
https://techcommunity.microsoft.com/t5/excel/tool-to-auto-fix-broken-excel-links-after-migration-to/m-p/290940
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