The system requires libGLX_indirect.so.0 to be available. This should be a symlink to libGLX_mesa.so.0
Took me quite a while to figure out, but I now have GLX on virtual NoMachine desktops
This is what you need to do:
Make sure you have the package libglx-mesa0 installed
cd /usr/lib/x86_64-linux-gnu/
ln -s libGLX_mesa.so.0 libGLX_indirect.so.0