Trying to load the service http://gis.ktimanet.gr/wms/ktbasemap/default.aspx and receives the message Could not understand the response. The wms provider said: Could not get WMS capabilities: error occurred while parsing reference at line 5 column 179 This is probably due to an incorrect WMS Server URL. Neither in http://gis.ktimanet.gr/wms/ktbasemap/default.aspx?SERVICE=WMS&REQUEST=GetCapabilities I have result.I never had a similar problem again with this service into something so simple
The web site for the online user is not the same adress as for the WMS service.
Following the last link on the entrance page https://www.ktimanet.gr/CitizenWebApp/Entrance_Page.aspx to https://www.ktimanet.gr/CitizenWebApp/Orthophotographs_Page.aspx I found this address:
which works in QGIS as WMS service.