I have a shapefile for a country and a shapefile representing the mobile network coverage of an operator in that country. I would like to create a shapefile that represents the parts of the country not covered by the mobile operator. I tried Symmetrical Difference which worked around the edges but that did not get at the internal gaps in the network coverage map.
You may try using the Symmetrical Difference SAGA tool from Processing: In the past I encountered some problems with the in-built algorithm, so you may do another attempt.
Before running the algorithm, make sure to activate the Processing Toolbox going to
Toolbox and then type Symmetrical difference in the search bar for quickly finding the algorithm:
It will work as the Symmetrical Difference tool which is in the core of QGIS: