How do I insert a link to a picture in Excel on Mac?

Using Microsoft Office 2021 Professional Plus on Windows 11 Pro, and Office 2021 for Mac Home and Business on Sequoia v15.4.1 for comparision, they are not implemented the same on both platforms.

On Windows, you can right-click on a given cell and the secondary menu will reveal a Link menu entry. On the Mac, that same menu entry is named Hyperlink. Both allow you to insert a link to a file in the respective filesystem. That link can be to a picture if needed, but that Mac link will not be portable to Windows users of Excel.

The Apple Support Community is not the best place for Microsoft product support. Try https://techcommunity.microsoft.com/category/microsoft365/discussions/excelgeneral.

For Numbers, Link to a webpage, email, phone number, or sheet in Numbers on Mac - Apple Support will point you in the right direction.

Excel is a Microsoft product. Contact Microsoft or check their user forums for support.