Today I found two tools from LinkTek that I want to share. First, the free one. LinkReporter is a free tool that reports on broken links throughout your IT enterprise. I suggest you run it and then decide to either fix the links manually or use a paid product to fix them for you.
The second tool is LinkFixer Advanced which runs against SharePoint on-premise, Microsoft 365, Box, OneDrive, DropBox, and regular file servers. It is an enterprise-wide application that appears to run against any of these platforms so it’s not specific to SharePoint at all.
For SharePoint-specific migrations, they offer a page which goes into more detail: LinkFixer Advanced for SharePoint. This could be the tool that saves your job or your sanity.