I have tried KDE in Qubes 4.1 (Thinkpad L390) and works very well. Regarding the small glitches about the icons, I have been doing some tests. What I have seen is that from Qube Manager > System > Global Settings > Window defaults > Tray icon mode… there are different options to display the icons associated with AppVMs (such as sys-net). I have tried them all:
default (thin border)
full background
thin border
thick border
tinted icon
tinted icon with modified white
tinted icon with 50% saturation
Full background
Network Manager icon: appears completely white.
Whonix icon: white background and the two circles in gray.
Thin border
Network Manager icon: appears completely red (the color of the AppVM).
Whonix icon: white background, the two circles in gray, and with a thin black border (the color of the AppVM).
Thick border
Network Manager icon: appears completely red (the color of the AppVM).
Whonix icon: white background, the two circles in gray, and with a thick black border (the color of the AppVM).
Tinted icon (with modified white or 50% saturation)
Network Manager icon: fully transparent.
Whonix icon: the two circles in gray, without a colored border, and the outer white is transparent. However, the pixels around the circles must not be pure white and no transparency is applied. Consequently, white dots are seen around the circles.
Default (thin border)
The result is the same a tinted icon.
I think the default option is not doing what it should (thin border).
And about the icon of the applications menu… in the configuration of the application launcher you can select a new icon. In System Icons > Applications there is “qubes-logo-icon” and “qubes-manager” and in the Places category there is the icon used in Xfce and available in four colors.
Personally, considering the problem with the NM icon, for the notification area icons I prefer the Thin border option. At least I can see the color of the NM icon. In any case, the KDE experience in Qubes has been very pleasant.
dnf list *plasma
kde-settings-plasma.noarch 2000:25-6.fc25.2
kf5-plsma 5.38…0-1.fc25
The network manager applets for any net vm are invisible since I installed KDE. It’s a pain, but I know where they are on the system tray so can find them blindly.
Unusually, after suspending and restarting the pc a few times over the course of a few days (without rebooting), maybe plugging in an external monitor, all the network manager applet icons appear in the system tray, colored red.
I can’t reproduce this behavior, it happens randomly. Maybe there’s a log file to check?
The fix suggested by h110w above, to replace the kde system tray widget with Stalonetray from the fedora repository seemed like too much of a risk of breaking my stock install.
KDE has been great otherwise and it seems like the issue is kind of resolved in 4.1
After a couple of weeks and playing around with KDE settings in dom0 I got some new experiences for this topic. I use the “Icons-Only Taskmanager Settings” and figured out that it is quite annoying to find another app in background when your taskmanager (or taskbar) is full of locks.
Even these applications have a ‘real’ icon when I search for them in launcher, but after starting the app it loses its Icon in taskmanager. When I pin the app to taskmanager it shows up like it should, but again, after starting it from taskmanager I got the lock again.
That brought me to a new idea… Maybe the reason for the missing icons are compatibility issues between gnome/xfce and kde? We installed kde desktop in dom0, but the templates are provided with gnome and gnome network manager, aren’t they?
so far, so good… I copied my productive fedora 34 template and tried to install kde-desktop
sudo dnf install @kde-desktop
and run into following:
No match for group package “k3b-extras-freeworld” No match for group package “plasma-workspace-xorg”
*Error: *
Problem: problem with installed package qubes-core-agent-4.0.63-1.fc34.x86_64*
package qubes-core-agent-4.0.63-1.fc34.x86_64 conflicts with firewalld provided by firewalld-0.9.3-2.fc34.noarch*
package qubes-core-agent-4.0.62-1.fc34.x86_64 conflicts with firewalld provided by firewalld-0.9.3-2.fc34.noarch*
package firewall-config-0.9.3-2.fc34.noarch requires firewalld = 0.9.3-2.fc34, but none of the providers can be installed*
conflicting requests*
package firewall-config-0.9.4-1.fc34.noarch requires firewalld = 0.9.4-1.fc34, but none of the providers can be installed*
package qubes-core-agent-4.0.63-1.fc34.x86_64 conflicts with firewalld provided by firewalld-0.9.4-1.fc34.noarch*
package qubes-core-agent-4.0.62-1.fc34.x86_64 conflicts with firewalld provided by firewalld-0.9.4-1.fc34.noarch* (try to add ‘–allowerasing’ to command line to replace conflicting packages or ‘–skip-broken’ to skip uninstallable packages)
I really think --allowerasing will brick the qubes-core-agent… I don’t have more time this weekend to test it anyway, but maybe this is a hint… The issues with qubes-core-agent confirm my thoughts… Probably there’s no solution for the locks, because they are surely caused by the qubes-core-agent, but Fedora seems to be a little overwhelming with installing packages and dependencies, so I thought about creating a standalone fedora vm with kde desktop and after this converting it to a template and install the qubes-core-agent? I still use RC4.0 with Fedora-34 Template
will come back to this and update my results
EDIT: I missed the fact, that the nm-applet is a gnome utility … Perhaps it got unistalled in dom0 when switching to kde? Would be interesting to know if its running as a service under xfce desktop. If yes, then installing kde desktop in the template won’t bring the applet back. But installing it in dom0 again would possibly do
Once are done installing, reboot. At the user login screen, choose “Plasma” in the top right of the screen. You can always revert back to xfce in the same manner.
Hey KDE gurus… I successfully installed KDE in Qubes 4.1 and I love it. One small issue that baffles me though…
Initially a mouseover on panel items would display the name and description of the item. For some reason that no longer occurs. I don’t see a setting for that anywhere. Any idea what could be causing this behavior?
In xfce, the panel launcher has a setting that allowed me to create a launcher drop down menu of icons… iow, a single icon on the panel with a ‘down arrow’ next to it. Click the arrow to display a column of app icons. For instance, this allowed me to have a single browser icon on the top panel with a drop down that had many browsers for numerous VMs. Same for terminals and other classes of apps.
The same set up does not seem possible in KDE. There is a "quick launcher’ widget, but that permanently displays the icons horizontally. Any ideas on how to create something similar to the xfce launcher?
The biggest issue I’ve had with KDE is how gtk based apps are displayed in the qt environment. This is mostly in dpi settings but things like displayed font sizes differ when flipping between apps, ex. firefox or terminals.
Great answers on here Sven. Thanks! KDE looks nicely.
Are there any security issues with this setup? Is everything open source code? I read about weak packages in the terminal…
Yes, everything is free and open-source. AFAIK, KDE has more lines of code to rely on, resulting in a slightly larger attack surface. But since dom0 is offline, it shouldn’t make a difference.
Sounds great! Looks very sweet. And i love the Qubes icons in 4.1. They are very clean! Goes nicely with KDE! Such an improvement in Qubes there. And other stuff… Really cool OS!
But i would want some kind of IDE though…
Want to learn how to install tripwire and snort in some untouched cube… So you would know if anyone has been hacking something.
I don’t think i would be hacked, but you don’t know until you sniff the traffic…
Has anyone tried Bismuth tiling manager for KDE? I am using krohnkite but there seems to be a newer better maintained option for kde but installing it seems to be quite different than other kwin scripts? I’d like to try it but it seems that for fedora/dom0 the option would be via copr?
… Perhaps it got unistalled in dom0 when switching to kde? Would be interesting to know if its running as a service under xfce desktop. If yes, then installing kde desktop in the template won’t bring the applet back. But installing it in dom0 again would possibly do 
And other stuff… Really cool OS!