https://bugzilla.redhat.com/show_bug.cgi?id=2179854
--- Comment #25 from Akira TAGOH tagoh@redhat.com --- You can't replace FcFontMatch with FcFontSort. I'm not sure if there are really any such code paths though, they set FC_FILE and FC_INDEX only when QFontEngine::FaceId has a filename. This implies that filename and index isn't always available; maybe application specific font?
Anyway, you still need to fallback to FcFontMatch in that case as I wrote it that way in my patch. Apparently you didn't seem to read it though.