In the pull request, @mvo noted a failure in one of the old core16 snaps:
I think what is happening here is that the Ubuntu 16.04 version of libGL tries to fall back to the swrast DRI driver. While that driver doesn’t require any special hardware to run, I suspect it relies on the X server running Mesa’s GLX code.
One thing that would be useful to try in cases like this would be to run the app with the environment variable LIBGL_ALWAYS_INDIRECT=true set (as documented here: https://docs.mesa3d.org/envvars.html). This should get the Mesa libGL to try indirect rendering (i.e. forward GL calls to the X server via GLX) instead of the swrast driver, which will hopefully avoid the segfault.
It won’t be as fast as direct rendering with the Nvidia binary drivers, but should be faster than software rendering. If this works, perhaps we can inject that environment variable when running these old snaps.