OK, and sorry for making you do all that. 
However, I have some new leads! 
First of all, I found a link in the snapcraft forum which will interest you:
Second, I was able to get a useful backtrace: (gdb) bt
#1 0x00007fffda628a7d in ?? () from /snap/cmake/323/usr/lib/x86_64-linux-gnu/dri/i965_dri.so
#2 0x00007fffda656843 in ?? () from /snap/cmake/323/usr/lib/x86_64-linux-gnu/dri/i965_dri.so
#3 0x00007fffda6c45e1 in ?? () from /snap/cmake/323/usr/lib/x86_64-linux-gnu/dri/i965_dri.so
#4 0x00007fffe86448f7 in ?? () from /snap/cmake/323/bin/../usr/lib/x86_64-linux-gnu/libGLX_mesa.so.0
#5 0x00007fffe8630f26 in ?? () from /snap/cmake/323/bin/../usr/lib/x86_64-linux-gnu/libGLX_mesa.so.0
#6 0x00007fffe862c7d2 in ?? () from /snap/cmake/323/bin/../usr/lib/x86_64-linux-gnu/libGLX_mesa.so.0
#7 0x00007fffe862df12 in ?? () from /snap/cmake/323/bin/../usr/lib/x86_64-linux-gnu/libGLX_mesa.so.0
#8 0x00007ffff30f6651 in glXChooseFBConfig () from /snap/cmake/323/bin/../usr/lib/x86_64-linux-gnu/libGLX.so.0
#9 0x00007fffeabfd0d8 in ?? () from /snap/cmake/323/usr/lib/x86_64-linux-gnu/qt5/plugins/xcbglintegrations/libqxcb-glx-integration.so
#10 0x00007fffeabfd47d in ?? () from /snap/cmake/323/usr/lib/x86_64-linux-gnu/qt5/plugins/xcbglintegrations/libqxcb-glx-integration.so
#11 0x00007fffeabf9430 in ?? () from /snap/cmake/323/usr/lib/x86_64-linux-gnu/qt5/plugins/xcbglintegrations/libqxcb-glx-integration.so
#12 0x00007fffefae7876 in QXcbWindow::create() () from /snap/cmake/323/usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/../../../libQt5XcbQpa.so.5
#13 0x00007fffefad1f3b in QXcbIntegration::createPlatformWindow(QWindow*) const () from /snap/cmake/323/usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/../../../libQt5XcbQpa.so.5
#14 0x00007ffff60af2fe in QWindowPrivate::create(bool, unsigned long long) () from /snap/cmake/323/bin/../usr/lib/x86_64-linux-gnu/libQt5Gui.so.5
#15 0x00007ffff769caed in QWidgetPrivate::create_sys(unsigned long long, bool, bool) () from /snap/cmake/323/bin/../usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#16 0x00007ffff769d1ad in QWidget::create(unsigned long long, bool, bool) () from /snap/cmake/323/bin/../usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#17 0x00007ffff76a9aa6 in QWidget::setVisible(bool) () from /snap/cmake/323/bin/../usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#18 0x000055555559bf28 in main ()