grygoryz, попробуйте sudo apt update && sudo apt install --reinstall gnome-terminal
если не помогает, проверьте содержимое файла /usr/share/applications/gnome-terminal.desktop. Он должен выглядеть так:[Desktop Entry]
Name=Terminal
Comment=Use the command line
Keywords=shell;prompt;command;commandline;cmd;
TryExec=gnome-terminal
Exec=gnome-terminal
Icon=utilities-terminal
Type=Application
X-GNOME-DocPath=gnome-terminal/index.html
X-GNOME-Bugzilla-Bugzilla=GNOME
X-GNOME-Bugzilla-Product=gnome-terminal
X-GNOME-Bugzilla-Component=BugBuddyBugs
X-GNOME-Bugzilla-Version=3.18.3
Categories=GNOME;GTK;System;TerminalEmulator;
StartupNotify=true
X-GNOME-SingleWindow=false
OnlyShowIn=GNOME;Unity;
Actions=New
X-Ubuntu-Gettext-Domain=gnome-terminal
[Desktop Action New]
Name=New Terminal
Exec=gnome-terminal
OnlyShowIn=Unity