Created attachment 103930 [details]
screenshot

I tried discover just after installing Kubuntu 16.04.1 LTS, and some software was being displayed, but search was not working. I tried to install muon, and did some software update (which seemed to work fine), and after that discover would not display any software at all. Updates still work. Muon works fine, except that search stops working after a while.
There are display issues on top of that, but that is not the worst problem. Having the default software used for installing software on Kubuntu fail completely is a rather big issue...
I tried uninstalling plasma-discover and muon, purging them, and reinstalling them, but that did not change anything.

Is there anything I can do to work around the bug ?

This is the output I get when starting it from the CLI:

log_attica_plugin: Loaded paths from config: (QUrl("http://download.kde.org/ocs/providers.xml"))
knewstuff: Initializing KNS3::Engine from ' "/etc/xdg/comic.knsrc" '
knewstuff: Loading KNewStuff3 config:  "/etc/xdg/comic.knsrc"
knewstuff: Categories:  ("Plasma Comic")
knewstuff: Using registry file:  "/home/damien/.local/share/knewstuff3/.knsregistry"
knewstuff: Loading KNS2 registry of files for the component:  ""
knewstuff: Cache read... entries:  0
knewstuff: loading providers from  "http://download.kde.org/ocs/providers.xml"
knewstuff: XmlLoader::load(): url:  QUrl("http://download.kde.org/ocs/providers.xml")
log_attica_plugin: Loaded paths from config: (QUrl("http://download.kde.org/ocs/providers.xml"))
knewstuff: Initializing KNS3::Engine from ' "/etc/xdg/plasmoids.knsrc" '
knewstuff: Loading KNewStuff3 config:  "/etc/xdg/plasmoids.knsrc"
knewstuff: Categories:  ("Plasma 5 Plasmoid")
knewstuff: Loading KNS2 registry of files for the component:  ""
knewstuff: Cache read... entries:  0
knewstuff: loading providers from  "http://download.kde.org/ocs/providers.xml"
knewstuff: XmlLoader::load(): url:  QUrl("http://download.kde.org/ocs/providers.xml")
log_attica_plugin: Loaded paths from config: (QUrl("http://download.kde.org/ocs/providers.xml"))
no providers for "/etc/xdg/comic.knsrc"
invalid kns backend!
no providers for "/etc/xdg/plasmoids.knsrc"
invalid kns backend!
knewstuff: XmlLoader::slotJobData()
knewstuff: XmlLoader::slotJobData()
knewstuff: --Xml Loader-START--
knewstuff: "<providers>\n    <provider>\n        <id>api.kde-look.org</id>\n        <location>https://api.kde-look.org/ocs/v1/</location>\n        <name>api.kde-look.org</name>\n        <icon>\n        https://api.kde-look.org/theme/flatui/img/new/O-standard-logo.png\n        </icon>\n        <termsofuse>https://api.kde-look.org/content/terms</termsofuse>\n        <register>https://api.kde-look.org/register</register>\n        <services>\n            <person ocsversion=\"1.6\"/>\n            <content ocsversion=\"1.6\"/>\n        </services>\n    </provider>\n</providers>\n"
knewstuff: --Xml Loader-END--
knewstuff: slotProvidersLoaded
knewstuff: Provider attributes:  ""
log_attica_plugin: No credentials found
knewstuff: Engine addProvider called with provider with id  "https://api.kde-look.org/ocs/v1/"
knewstuff: XmlLoader::slotJobData()
knewstuff: XmlLoader::slotJobData()
knewstuff: --Xml Loader-START--
knewstuff: "<providers>\n    <provider>\n        <id>api.kde-look.org</id>\n        <location>https://api.kde-look.org/ocs/v1/</location>\n        <name>api.kde-look.org</name>\n        <icon>\n        https://api.kde-look.org/theme/flatui/img/new/O-standard-logo.png\n        </icon>\n        <termsofuse>https://api.kde-look.org/content/terms</termsofuse>\n        <register>https://api.kde-look.org/register</register>\n        <services>\n            <person ocsversion=\"1.6\"/>\n            <content ocsversion=\"1.6\"/>\n        </services>\n    </provider>\n</providers>\n"
knewstuff: --Xml Loader-END--
knewstuff: slotProvidersLoaded
knewstuff: Provider attributes:  ""
log_attica_plugin: No credentials found
knewstuff: Engine addProvider called with provider with id  "https://api.kde-look.org/ocs/v1/"
knewstuff: providerInitialized "api.kde-look.org"
knewstuff: providers loaded
knewstuff: providerInitialized "api.kde-look.org"
knewstuff: providers loaded