I have a text formula that uses the HYPERLINK function to create a clickable link. Exporting this via a report to an Excel file seemed to work for most data, but not all.
In the Salesforce report itself, all links work. In the exported Excel file, links that contain space characters do not work: they are simply not clickable, just displayed as text.
Example of such a URL:
https://some.domain.com/Path that has a space/img.png