How do I remove extra Skype icon or ghost icons for removed apps from GNOME shell?
Solution 1:
It seems you have snap installed as per your reply to @Carl's question.
Installing Skype from two sources (snap and .deb) lead to some junk .desktop files after removing the snap package. You can solve this by cleaning up after removing the snap.
Check the /var/lib/snapd/desktop/applications/ directory for a skype_forlinux.desktop file or something with skype* in the name (or any .desktop file which may be associated to the application). If you find it, move it somewhere else (e.g. /tmp) and check again by searching though 'Activities'.
It should be fine now.