To stop Alerts for broken links appearing within Excel, the following steps need to be taken on a Windows device.

Click Data > Edit Links, see screenshot:
doc-disable-update-links-1
2. In the Edit Links dialog box, click Startup Prompt button at the bottom, see screenshot:
doc-disable-update-links-1
3. And then in the popped out Startup Prompt dialog, you can choose Don’t display the alert and don’t update automatic links or Don’t display the alert and update links as you need.
doc-disable-update-links-1
4. Then click OK, and close the former dialog box, and when you open this workbook next time, the Update Links message will not appear any more.