This sounds like a bug in the snap. The github-desktop snap uses classic confinement, so it can see the host system’s file system. This usually means it needs to be compiled in a way that it will pick bundled libraries in preference to the host system libraries, and that appears that hasn’t happened here.
In this particular case either github-desktop or a host system library it has loaded is trying to use the g_date_copy symbol, but the libglib-2.0.so.0 it has loaded doesn’t provide it. According to the docs, the symbol was added in 2.56.
As a classic snap, it then picks the library from the host system. That library happens to use the g_date_copy symbol that doesn’t exist in the bundled libglib-2.0.so.0 and things explode.
CC’ing @popey and @Wimpress since this snap is published by snapcrafters. Is this something you guys worked on?
any update about it? i just installed this snap on a fresh ubuntu 18.04.3 installation and got the same error. github-desktop not starting. any chance, that the maintainer will update the snap as it doesnt work since months now?