Gnome on Ubuntu 18.04 is crashing after logging in

I figured it out. It was problem with GNOME extension called Unite. After disabling it problem still occurred, so I had to completely remove it.

rm -rf ~/.local/share/gnome-shell/extensions/[email protected]

did the job :)

As suggested, you can remove all files of the offending extension.

You could also go a less invasive way (particular in case you are not sure if an extension is the problem)

1. list all extension names via ls ~/.local/share/gnome-shell/extensions to find the full name (including the url-part after the @)
2. disable the extension via gnome-shell-extension-tool -d [email protected] e.g. gnome-shell-extension-tool -d [email protected]
3. You enable the extension again using -e (like enable) instead of -d (as disable)

…which I know from "How to activate/deactivate a gnome-shell extension from command line"

In case you want to check if any extension causes your problem, you could also enable/disable them all and then do the above for a more detailed diagnosis:

gsettings set org.gnome.shell disable-user-extensions true (and, to restore the previous state, use false instead of true) (source)