@JKSH Seems you were correct :
QML debugging is enabled. Only use this in a safe environment.
Info: Starting QML Puppet ((null):0, (null))
Info: Could not load the Qt platform plugin "xcb" in "" even though it was found. ((null):0, (null))
Fatal: This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.
Available platform plugins are: wayland, offscreen, minimal, wayland-egl, xcb, linuxfb, minimalegl, vnc, vkkhrdisplay, eglfs.
((null):0, (null))
ldd returns :
linux-vdso.so.1 (0x00007ffed5dfb000)
libQt6XcbQpa.so.6 => /home/user/Qt/Tools/QtDesignStudio/qt6_design_studio_reduced_version/plugins/platforms/./../../lib/libQt6XcbQpa.so.6 (0x00007f3bda977000)
libxkbcommon-x11.so.0 => /lib/x86_64-linux-gnu/libxkbcommon-x11.so.0 (0x00007f3bda955000)
libxkbcommon.so.0 => /lib/x86_64-linux-gnu/libxkbcommon.so.0 (0x00007f3bda90f000)
libxcb-cursor.so.0 => not found
libxcb-icccm.so.4 => /lib/x86_64-linux-gnu/libxcb-icccm.so.4 (0x00007f3bda908000)
libxcb-image.so.0 => /lib/x86_64-linux-gnu/libxcb-image.so.0 (0x00007f3bda900000)
libxcb-keysyms.so.1 => /lib/x86_64-linux-gnu/libxcb-keysyms.so.1 (0x00007f3bda8fb000)
libxcb-randr.so.0 => /lib/x86_64-linux-gnu/libxcb-randr.so.0 (0x00007f3bda8e9000)
libxcb-render-util.so.0 => /lib/x86_64-linux-gnu/libxcb-render-util.so.0 (0x00007f3bda8e2000)
libxcb-shm.so.0 => /lib/x86_64-linux-gnu/libxcb-shm.so.0 (0x00007f3bda8dd000)
libxcb-sync.so.1 => /lib/x86_64-linux-gnu/libxcb-sync.so.1 (0x00007f3bda8d4000)
libxcb-xfixes.so.0 => /lib/x86_64-linux-gnu/libxcb-xfixes.so.0 (0x00007f3bda8c9000)
libxcb-render.so.0 => /lib/x86_64-linux-gnu/libxcb-render.so.0 (0x00007f3bda8bb000)
libxcb-shape.so.0 => /lib/x86_64-linux-gnu/libxcb-shape.so.0 (0x00007f3bda8b6000)
libxcb-xkb.so.1 => /lib/x86_64-linux-gnu/libxcb-xkb.so.1 (0x00007f3bda898000)
libxcb.so.1 => /lib/x86_64-linux-gnu/libxcb.so.1 (0x00007f3bda86e000)
libQt6OpenGL.so.6 => /home/user/Qt/Tools/QtDesignStudio/qt6_design_studio_reduced_version/plugins/platforms/./../../lib/libQt6OpenGL.so.6 (0x00007f3bda7cc000)
libQt6Gui.so.6 => /home/user/Qt/Tools/QtDesignStudio/qt6_design_studio_reduced_version/plugins/platforms/./../../lib/libQt6Gui.so.6 (0x00007f3bd9e00000)
libGL.so.1 => /lib/x86_64-linux-gnu/libGL.so.1 (0x00007f3bd9d79000)
libQt6Core.so.6 => /home/user/Qt/Tools/QtDesignStudio/qt6_design_studio_reduced_version/plugins/platforms/./../../lib/libQt6Core.so.6 (0x00007f3bd9600000)
libX11-xcb.so.1 => /lib/x86_64-linux-gnu/libX11-xcb.so.1 (0x00007f3bda7c5000)
libX11.so.6 => /lib/x86_64-linux-gnu/libX11.so.6 (0x00007f3bd94c2000)
libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f3bd9d72000)
libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f3bd9d6d000)
libstdc++.so.6 => /lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f3bd9200000)
libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f3bd9117000)
libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f3bd9d49000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f3bd8e00000)
libxcb-cursor.so.0 => not found
libglib-2.0.so.0 => /lib/x86_64-linux-gnu/libglib-2.0.so.0 (0x00007f3bd8cb9000)
libgthread-2.0.so.0 => /lib/x86_64-linux-gnu/libgthread-2.0.so.0 (0x00007f3bd9d42000)
libxcb-util.so.1 => /lib/x86_64-linux-gnu/libxcb-util.so.1 (0x00007f3bd9d39000)
libXau.so.6 => /lib/x86_64-linux-gnu/libXau.so.6 (0x00007f3bd9d33000)
libXdmcp.so.6 => /lib/x86_64-linux-gnu/libXdmcp.so.6 (0x00007f3bd9d29000)
libEGL.so.1 => /lib/x86_64-linux-gnu/libEGL.so.1 (0x00007f3bd9d16000)
libfontconfig.so.1 => /lib/x86_64-linux-gnu/libfontconfig.so.1 (0x00007f3bd9cc8000)
libQt6DBus.so.6 => /home/user/Qt/Tools/QtDesignStudio/qt6_design_studio_reduced_version/plugins/platforms/./../../lib/libQt6DBus.so.6 (0x00007f3bd9051000)
libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f3bd9caa000)
libfreetype.so.6 => /lib/x86_64-linux-gnu/libfreetype.so.6 (0x00007f3bd8bef000)
libGLdispatch.so.0 => /lib/x86_64-linux-gnu/libGLdispatch.so.0 (0x00007f3bd8b37000)
libGLX.so.0 => /lib/x86_64-linux-gnu/libGLX.so.0 (0x00007f3bd9490000)
libicui18n.so.56 => /home/user/Qt/Tools/QtDesignStudio/qt6_design_studio_reduced_version/plugins/platforms/./../../lib/libicui18n.so.56 (0x00007f3bd8600000)
libicuuc.so.56 => /home/user/Qt/Tools/QtDesignStudio/qt6_design_studio_reduced_version/plugins/platforms/./../../lib/libicuuc.so.56 (0x00007f3bd8200000)
libicudata.so.56 => /home/user/Qt/Tools/QtDesignStudio/qt6_design_studio_reduced_version/plugins/platforms/./../../lib/libicudata.so.56 (0x00007f3bd6800000)
librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f3bd9ca1000)
/lib64/ld-linux-x86-64.so.2 (0x00007f3bdaa32000)
libpcre2-8.so.0 => /lib/x86_64-linux-gnu/libpcre2-8.so.0 (0x00007f3bd8a9d000)
libbsd.so.0 => /lib/x86_64-linux-gnu/libbsd.so.0 (0x00007f3bd9c8c000)
libexpat.so.1 => /lib/x86_64-linux-gnu/libexpat.so.1 (0x00007f3bd9026000)
libdbus-1.so.3 => /lib/x86_64-linux-gnu/libdbus-1.so.3 (0x00007f3bd67b2000)
libpng16.so.16 => /lib/x86_64-linux-gnu/libpng16.so.16 (0x00007f3bd85c8000)
libbrotlidec.so.1 => /lib/x86_64-linux-gnu/libbrotlidec.so.1 (0x00007f3bd9483000)
libmd.so.0 => /lib/x86_64-linux-gnu/libmd.so.0 (0x00007f3bd9476000)
libsystemd.so.0 => /lib/x86_64-linux-gnu/libsystemd.so.0 (0x00007f3bd66e2000)
libbrotlicommon.so.1 => /lib/x86_64-linux-gnu/libbrotlicommon.so.1 (0x00007f3bd66bf000)
libcap.so.2 => /lib/x86_64-linux-gnu/libcap.so.2 (0x00007f3bd901a000)
libgcrypt.so.20 => /lib/x86_64-linux-gnu/libgcrypt.so.20 (0x00007f3bd6577000)
liblzma.so.5 => /lib/x86_64-linux-gnu/liblzma.so.5 (0x00007f3bd6545000)
libzstd.so.1 => /lib/x86_64-linux-gnu/libzstd.so.1 (0x00007f3bd6491000)
liblz4.so.1 => /lib/x86_64-linux-gnu/liblz4.so.1 (0x00007f3bd646e000)
libgpg-error.so.0 => /lib/x86_64-linux-gnu/libgpg-error.so.0 (0x00007f3bd6448000)
I installed libxcb-cursor and the problem is solved, thanks a lot !
