I stumbled over this issue with various Qt5 applications on Debian Sid, too, and had initially reported my issue here:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=818232 Switching the VNC viewer does not seem to help, I tried xtightvncviewer and krdc. Not only the TightVNC server, but also the RealVNC one (vnc4server package) seem to be affected. TigerVNC on the other hand works like a charm (which is my current workaround for this issue for now). Noticeably, on TightVNC and RealVNC, I get this error message, while on TigerVNC I don't: "Qt: XKEYBOARD extension not present on the X server." So looks like James initial investigations lead to the right direction. Unfortunately, this report on the Qt bugtracker indicates that it was closed and deemed "out of scope" and that VNC servers should implement this XKEYBOARD extension :-( : https://bugreports.qt.io/browse/QTBUG-44938 This ticket also has some nice explanations why Qt5 has this issue and Qt4 doesn't (e.g. the preference of libxkbcommon over xlib in Qt5). Regards, Linus
