I flew UK to the Balkans recently and would like to propose updating a few email addresses for airports which are either missing or intended for general public enquiries rather than the operations teams or ATC that GA pilots would normally deal with.
The only country that required an overflight permit from the local authorities was in North Macedonia. I don't know if its possible to flag that up as a warning (similar to notifying about GAR forms, flight plans etc when crossing borders). It was fairly easy to obtain by emailing the appropriate aircraft documents.