Ideally there would be a service that expands on what downinspector.com does. Something that tries to access an URL from various kinds of IPs (CGNAT, Tor, VPNs, public libraries, various regions) to establish whether or not the file is reachable by all people. Then ideally lemmy could be coded to treat links based on whether exclusivity is detected.
In principle this would be in the domain of the #OONI project. But I doubt they have anything like this. E.g. OONI tracks whether a country blocks a domain (explorer.ooni.org/domains), but not whether a domain blocks a country.