今天我遇到了一个奇怪的问题。在通知面板上单击“您有更新”图标后，发现更新了源，找到了内核更新，然后……什么都没有。按钮update all至少 20 秒没有出现，所以我关闭了发现，单击了通知，结果还是一样。所以最后我从终端启动了发现，看看它是否抛出了任何错误。
有很多！TypeError 之前的文本很快就出现了，update all当我在 ubuntu 的 bugzilla 中搜索错误消息时，其余消息以及缺失的 都出现了。不过，这方面没有运气。我确实找到了一个建议我需要重新安装 discover 。我运行了
sudo apt install --reinstall plasma-discover，但 discover 之后并没有恢复到正常速度。
user@laptop:~$ plasma-discover
adding empty sources model QStandardItemModel(0x563937bbc640)
no packages for "org.kde.plasma.quicklaunch"
no packages for "org.kde.plasma.systemloadviewer"
no packages for "android-sdk"
no packages for "org.kde.plasma.showActivityManager"
no packages for "libgphoto2"
no packages for "org.kde.plasma.grouping"
no packages for "org.kde.plasma.diskquota"
no packages for "org.kde.plasma.timer"
no packages for "org.kde.kscreen"
no packages for "libu2f-udev"
no packages for "org.kde.plasma.appmenu"
no packages for "im.riot.webapp"
no packages for "org.kde.plasma.kimpanel"
no packages for "org.cockpit_project.cockpit"
invalid kns backend! "/usr/share/knsrcfiles/ksysguard.knsrc" because: "Config group not found! Check your KNS3 installation."
took really long to fetch KNSBackend(0x563939dddc40, name = "/usr/share/knsrcfiles/window-decorations.knsrc")
took really long to fetch KNSBackend(0x56393a03b2d0, name = "/usr/share/knsrcfiles/cgctheme.knsrc")
took really long to fetch KNSBackend(0x563939de83a0, name = "/usr/share/knsrcfiles/icons.knsrc")
took really long to fetch KNSBackend(0x563939de81e0, name = "/usr/share/knsrcfiles/cgcgtk3.knsrc")
took really long to fetch KNSBackend(0x563939682350, name = "/usr/share/knsrcfiles/aurorae.knsrc")
took really long to fetch KNSBackend(0x5639396975d0, name = "/usr/share/knsrcfiles/emoticons.knsrc")
took really long to fetch KNSBackend(0x56393969aaf0, name = "/usr/share/knsrcfiles/kwinswitcher.knsrc")
took really long to fetch KNSBackend(0x56393967f8d0, name = "/usr/share/knsrcfiles/discover_ktexteditor_codesnippets_core.knsrc")
took really long to fetch KNSBackend(0x563939690a80, name = "/usr/share/knsrcfiles/kwineffect.knsrc")
took really long to fetch KNSBackend(0x5639396943a0, name = "/usr/share/knsrcfiles/kwinscripts.knsrc")
took really long to fetch KNSBackend(0x563939694940, name = "/usr/share/knsrcfiles/sddmtheme.knsrc")
took really long to fetch KNSBackend(0x56393967fb20, name = "/usr/share/knsrcfiles/wallpaperplugin.knsrc")
took really long to fetch KNSBackend(0x56393969b900, name = "/usr/share/knsrcfiles/wallpaper.knsrc")
took really long to fetch KNSBackend(0x5639396a42a0, name = "/usr/share/knsrcfiles/lookandfeel.knsrc")
took really long to fetch KNSBackend(0x5639396b11f0, name = "/usr/share/knsrcfiles/plasma-themes.knsrc")
took really long to fetch KNSBackend(0x5639396a9140, name = "/usr/share/knsrcfiles/xcursor.knsrc")
took really long to fetch KNSBackend(0x563939695b80, name = "/usr/share/knsrcfiles/comic.knsrc")
took really long to fetch KNSBackend(0x56393969ccc0, name = "/usr/share/knsrcfiles/plasmoids.knsrc")
took really long to fetch KNSBackend(0x5639396a7490, name = "/usr/share/knsrcfiles/colorschemes.knsrc")
took really long to fetch KNSBackend(0x56393969f630, name = "/usr/share/knsrcfiles/ksplash.knsrc")
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/ScrollablePage.qml:187: TypeError: Cannot assign to read-only property "parent"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/ScrollablePage.qml:187: TypeError: Cannot assign to read-only property "parent"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/ScrollablePage.qml:187: TypeError: Cannot assign to read-only property "parent"
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/ScrollablePage.qml:187: TypeError: Cannot assign to read-only property "parent"
invalid kns backend! "/usr/share/knsrcfiles/window-decorations.knsrc" because: "Backend Window Decorations took too long to initialise"
org.kde.plasma.libdiscover: Discarding invalid backend "window-decorations.knsrc"
invalid kns backend! "/usr/share/knsrcfiles/icons.knsrc" because: "Backend Icons took too long to initialise"
org.kde.plasma.libdiscover: Discarding invalid backend "icons.knsrc"
invalid kns backend! "/usr/share/knsrcfiles/aurorae.knsrc" because: "Backend Aurorae Window Decorations took too long to initialise"
org.kde.plasma.libdiscover: Discarding invalid backend "aurorae.knsrc"
invalid kns backend! "/usr/share/knsrcfiles/emoticons.knsrc" because: "Backend Emoticons took too long to initialise"
org.kde.plasma.libdiscover: Discarding invalid backend "emoticons.knsrc"
invalid kns backend! "/usr/share/knsrcfiles/kwinswitcher.knsrc" because: "Backend Window Manager Switching Layouts took too long to initialise"
org.kde.plasma.libdiscover: Discarding invalid backend "kwinswitcher.knsrc"
invalid kns backend! "/usr/share/knsrcfiles/discover_ktexteditor_codesnippets_core.knsrc" because: "Backend Kate Snippets took too long to initialise"
org.kde.plasma.libdiscover: Discarding invalid backend "discover_ktexteditor_codesnippets_core.knsrc"
invalid kns backend! "/usr/share/knsrcfiles/kwineffect.knsrc" because: "Backend Window Manager Effects took too long to initialise"
org.kde.plasma.libdiscover: Discarding invalid backend "kwineffect.knsrc"
invalid kns backend! "/usr/share/knsrcfiles/kwinscripts.knsrc" because: "Backend Window Manager Scripts took too long to initialise"
org.kde.plasma.libdiscover: Discarding invalid backend "kwinscripts.knsrc"
invalid kns backend! "/usr/share/knsrcfiles/sddmtheme.knsrc" because: "Backend Login Screen took too long to initialise"
org.kde.plasma.libdiscover: Discarding invalid backend "sddmtheme.knsrc"
invalid kns backend! "/usr/share/knsrcfiles/wallpaperplugin.knsrc" because: "Backend Wallpaper Plugins took too long to initialise"
org.kde.plasma.libdiscover: Discarding invalid backend "wallpaperplugin.knsrc"
invalid kns backend! "/usr/share/knsrcfiles/wallpaper.knsrc" because: "Backend Wallpapers took too long to initialise"
org.kde.plasma.libdiscover: Discarding invalid backend "wallpaper.knsrc"
invalid kns backend! "/usr/share/knsrcfiles/lookandfeel.knsrc" because: "Backend Look and Feel took too long to initialise"
org.kde.plasma.libdiscover: Discarding invalid backend "lookandfeel.knsrc"
invalid kns backend! "/usr/share/knsrcfiles/plasma-themes.knsrc" because: "Backend Plasma Themes took too long to initialise"
org.kde.plasma.libdiscover: Discarding invalid backend "plasma-themes.knsrc"
invalid kns backend! "/usr/share/knsrcfiles/xcursor.knsrc" because: "Backend Cursors took too long to initialise"
org.kde.plasma.libdiscover: Discarding invalid backend "xcursor.knsrc"
invalid kns backend! "/usr/share/knsrcfiles/comic.knsrc" because: "Backend Comics took too long to initialise"
org.kde.plasma.libdiscover: Discarding invalid backend "comic.knsrc"
invalid kns backend! "/usr/share/knsrcfiles/plasmoids.knsrc" because: "Backend Plasma Widgets took too long to initialise"
org.kde.plasma.libdiscover: Discarding invalid backend "plasmoids.knsrc"
invalid kns backend! "/usr/share/knsrcfiles/colorschemes.knsrc" because: "Backend Colour Schemes took too long to initialise"
org.kde.plasma.libdiscover: Discarding invalid backend "colorschemes.knsrc"
invalid kns backend! "/usr/share/knsrcfiles/ksplash.knsrc" because: "Backend Splash Screens took too long to initialise"
org.kde.plasma.libdiscover: Discarding invalid backend "ksplash.knsrc"
那么，有人知道问题是什么吗？我尝试搜索 kns，但除了 之外没有找到任何其他包knot-dnsutils。由于其描述不符合错误，我假设缺少的 KNSBackend 是另一个包的一部分。
虽然更新有效，但我对更新所花的时间不满意，我想知道如何修复它。如果有帮助的话，我很乐意提供更多详细信息。我的 Kubuntu 19.10 最初安装为 18.04 或 18.10 并进行了 dist-upgrade，我使用的是 amd64 cpu 架构。我的设置中唯一不寻常的事情是 Ubuntu 开发人员可能不会经常测试我已经清除snapd并删除了plasma-discover-snap-backend。
其他所需信息：
user@laptop:~$ plasma-discover --version
discover 5.16.5