I'm not sure "the most stable desktop environment" is a simple matter because of the dependencies involved. The desktop enviroment depends on the underlying GUI, xorg or wayland, as well as the toolkits that form them. Running debian testing some time ago on a machine here, the desktop crashed with xorg problems rather than desktop problems, but it took some investigation to discover that it wasn't the desktop software itself. More stable than running a desktop environment is running a robust window manager. Window managers are much smaller in code and less complex. That's not to say that they can't also crash, but the risks are statistically in their favour and lots of them have very robust histories. They also make far fewer demands on memory and computer resources generally but have fewer facilities and capabilities than the full-on desktop environments. That limitation means that the user has to know how to get around the system using discrete utilities they seek out and perhaps lots more command line usage. However, that said, the reliability of modern desktop environments is very seductive with modern hardware that handles it so seamlessly.