Further testing shows that there are two separate problematic global Qt environment settings in /etc/profile.d/edubuntu-qt.sh on Edubuntu 26.04 (and persisting in to 26.06.1 LT):
export QT_STYLE_OVERRIDE=kvantum export QT_QPA_PLATFORM=xcb The system is running a Wayland GNOME session. 1. QT_QPA_PLATFORM=xcb This forces Qt applications to use X11/XCB despite the desktop session being Wayland. For example, the KWrite Flatpak (org.kde.kwrite) fails to start with: qt.qpa.xcb: could not connect to display qt.qpa.plugin: Could not load the Qt platform plugin "xcb" KWrite starts correctly when the variable is removed: env -u QT_QPA_PLATFORM flatpak run org.kde.kwrite 2. QT_STYLE_OVERRIDE=kvantum This causes problems with several Qt 6/KDE applications supplied by Ubuntu. KHangMan fails to start with: QQmlApplicationEngine failed to load component qrc:/qt/qml/org/kde/khangman/qml/Main.qml: module "kvantum" is not installed It starts normally with: env -u QT_STYLE_OVERRIDE khangman KBruch and KMPlot also display incorrectly with the global Kvantum style override and work normally when launched with QT_STYLE_OVERRIDE unset. I have reproduced this consistently. As a system-wide workaround I have changed /etc/profile.d/edubuntu-qt.sh to: export QT_QPA_PLATFORMTHEME=kvantum # export QT_STYLE_OVERRIDE=kvantum # export QT_QPA_PLATFORM=xcb After starting a fresh user session with those two variables unset: KWrite Flatpak launches normally KHangMan launches normally KBruch renders normally KMPlot renders normally QT_QPA_PLATFORMTHEME=kvantum has been left unchanged and has not been implicated by these tests. I suggest that edubuntu-artwork should not globally export QT_QPA_PLATFORM=xcb or QT_STYLE_OVERRIDE=kvantum on current Edubuntu/Ubuntu Wayland sessions. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2163613 Title: QT_QPA_PLATFORM=xcb prevents Qt Flatpak apps launching on Wayland To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/edubuntu-artwork/+bug/2163613/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
