I installed Qt5.7 including the Qtcreator using the installation tool "qt-unified-linux-x64-3.0.5-online.run" into the folder /usr/local/Qt
When I run qtcreator in verbose mode (export QT_DEBUG_PLUGINS=1), I get the following output:
Cannot load library /usr/local/Qt/5.7/gcc_64/plugins/platforms/libqxcb.so: (/usr/local/Qt/5.7/gcc_64/lib/libQt5XcbQpa.so.5: symbol _ZTI18QPlatformClipboard, version Qt_5 not defined in file libQt5Gui.so.5 with link time reference)
QLibraryPrivate::loadPlugin failed on "/usr/local/Qt/5.7/gcc_64/plugins/platforms/libqxcb.so" : "Cannot load library /usr/local/Qt/5.7/gcc_64/plugins/platforms/libqxcb.so: (/usr/local/Qt/5.7/gcc_64/lib/libQt5XcbQpa.so.5: symbol _ZTI18QPlatformClipboard, version Qt_5 not defined in file libQt5Gui.so.5 with link time reference)"
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.
Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, xcb, vnc.
Running ldd /usr/local/Qt/5.7/gcc_64/plugins/platforms/libqxcb.so returns
linux-vdso.so.1 => (0x00007ffdda390000)
libQt5XcbQpa.so.5 => /usr/local/Qt/5.7/gcc_64/lib/libQt5XcbQpa.so.5 (0x00007f9e44a33000)
libX11-xcb.so.1 => /usr/lib/x86_64-linux-gnu/libX11-xcb.so.1 (0x00007f9e44831000)
libXi.so.6 => /usr/lib/x86_64-linux-gnu/libXi.so.6 (0x00007f9e44621000)
libSM.so.6 => /usr/lib/x86_64-linux-gnu/libSM.so.6 (0x00007f9e44419000)
libICE.so.6 => /usr/lib/x86_64-linux-gnu/libICE.so.6 (0x00007f9e441ff000)
libdbus-1.so.3 => /lib/x86_64-linux-gnu/libdbus-1.so.3 (0x00007f9e43fb3000)
libxcb.so.1 => /usr/lib/x86_64-linux-gnu/libxcb.so.1 (0x00007f9e43d91000)
libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f9e43b8d000)
libgthread-2.0.so.0 => /usr/lib/x86_64-linux-gnu/libgthread-2.0.so.0 (0x00007f9e4398b000)
librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f9e43783000)
libglib-2.0.so.0 => /lib/x86_64-linux-gnu/libglib-2.0.so.0 (0x00007f9e43472000)
libXrender.so.1 => /usr/lib/x86_64-linux-gnu/libXrender.so.1 (0x00007f9e43268000)
libXext.so.6 => /usr/lib/x86_64-linux-gnu/libXext.so.6 (0x00007f9e43056000)
libX11.so.6 => /usr/lib/x86_64-linux-gnu/libX11.so.6 (0x00007f9e42d1c000)
libfontconfig.so.1 => /usr/lib/x86_64-linux-gnu/libfontconfig.so.1 (0x00007f9e42ad9000)
libfreetype.so.6 => /usr/lib/x86_64-linux-gnu/libfreetype.so.6 (0x00007f9e4282f000)
libEGL.so.1 => /usr/lib/nvidia-384/libEGL.so.1 (0x00007f9e4262a000)
libQt5Gui.so.5 => /usr/local/Qt/5.7/gcc_64/lib/libQt5Gui.so.5 (0x00007f9e41e9e000)
libQt5DBus.so.5 => /usr/local/Qt/5.7/gcc_64/lib/libQt5DBus.so.5 (0x00007f9e41c1e000)
libQt5Core.so.5 => /usr/local/Qt/5.7/gcc_64/lib/libQt5Core.so.5 (0x00007f9e41500000)
libGL.so.1 => /usr/lib/nvidia-384/libGL.so.1 (0x00007f9e411be000)
libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f9e40fa1000)
libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f9e40c1f000)
libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f9e40916000)
libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f9e40700000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f9e40336000)
libuuid.so.1 => /lib/x86_64-linux-gnu/libuuid.so.1 (0x00007f9e40131000)
libsystemd.so.0 => /lib/x86_64-linux-gnu/libsystemd.so.0 (0x00007f9e450fc000)
libXau.so.6 => /usr/lib/x86_64-linux-gnu/libXau.so.6 (0x00007f9e3ff2d000)
libXdmcp.so.6 => /usr/lib/x86_64-linux-gnu/libXdmcp.so.6 (0x00007f9e3fd27000)
/lib64/ld-linux-x86-64.so.2 (0x00007f9e44f84000)
libpcre.so.3 => /lib/x86_64-linux-gnu/libpcre.so.3 (0x00007f9e3fab7000)
libexpat.so.1 => /lib/x86_64-linux-gnu/libexpat.so.1 (0x00007f9e3f88e000)
libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f9e3f674000)
libpng12.so.0 => /usr/lib/x86_64-linux-gnu/libpng12.so.0 (0x00007f9e3f44f000)
libGLdispatch.so.0 => /usr/lib/nvidia-384/libGLdispatch.so.0 (0x00007f9e3f181000)
libicui18n.so.56 => /usr/local/Qt/5.7/gcc_64/lib/libicui18n.so.56 (0x00007f9e3ece7000)
libicuuc.so.56 => /usr/local/Qt/5.7/gcc_64/lib/libicuuc.so.56 (0x00007f9e3e92f000)
libicudata.so.56 => /usr/local/Qt/5.7/gcc_64/lib/libicudata.so.56 (0x00007f9e3cf4c000)
libnvidia-tls.so.384.130 => /usr/lib/nvidia-384/tls/libnvidia-tls.so.384.130 (0x00007f9e3cd48000)
libnvidia-glcore.so.384.130 => /usr/lib/nvidia-384/libnvidia-glcore.so.384.130 (0x00007f9e3ae8c000)
libselinux.so.1 => /lib/x86_64-linux-gnu/libselinux.so.1 (0x00007f9e3ac6a000)
liblzma.so.5 => /lib/x86_64-linux-gnu/liblzma.so.5 (0x00007f9e3aa48000)
libgcrypt.so.20 => /lib/x86_64-linux-gnu/libgcrypt.so.20 (0x00007f9e3a767000)
libgpg-error.so.0 => /lib/x86_64-linux-gnu/libgpg-error.so.0 (0x00007f9e3a553000)
I can't pin the error. Relevant threads are for example https://forum.qt.io/topic/71369/failed-to-load-qt-platform-plugin-xcb/2, but libQt5XcbQpa.so.5.6.1 is not missing in my case. Any ideas?