Microsoft Search: country-targeted bookmarks

If you have country-specific content – Microsoft Search allows bookmarks to be configured to pop-up only for users from a specific country.

But it does not work (or works only for US). What is problem? How do we troubleshoot it? How can we simulate user to be located in a specific country?

How does Microsoft define “this user is from that country”. What are the criteria to correlate User <-> Country? Physical IP address? License assigned country? Locale? Browser settings? Azure AD properties?

Any ideas/experience will be appreciated.
Please let me know.