Após instalar a versão -5.1-5.1.24 do Virtual Box para Linux 64 Bits, recebi o erro
xkbcommon: ERROR: failed to add default include path /usr/share/X11/xkb
Qt WARNING: Qt: Failed to create XKB context!
Qt WARNING: Use QT_XKB_CONFIG_ROOT environmental variable to provide an additional search path, add ':' as separator to provide several search paths and/or make sure that XKB configuration data directory contains recent enough contents, to update please see http://cgit.freedesktop.org/xkeyboard-config/ .
Qt WARNING: QXcbConnection: XCB error: 145 (Unknown), sequence: 171, resource id: 0, major code: 139 (Unknown), minor code: 20
Solução de contorno: export QT_XKB_CONFIG_ROOT=/usr/share/X11/xkb