Nominatim searches in Marble 2.2.20 (KDE Applications 17.12.1) recently stopped working. On the console, the warning:
Cannot parse osm nominatim result
is printed. No results appear.
I suspect that this is because http://nominatim.openstreetmap.org/ now redirects to https://nominatim.openstreetmap.org/ , so the URL fragment at OsmNominatimSearchRunner.cpp:53 needs to be updated. And you probably also want to fix your code to support redirects.
*** This bug has been marked as a duplicate of bug 394517 ***