Keep only one Gnome-Terminal instance (Ubuntu 22.04) | Breakertt Blog

Method 1 - Remap gnome dock shortcut

1. Add gnome-terminal into dock (favortie), I move it to the third application, please change the number 3 in following article to the number you used.
2. Disable terminal shortcut in Settings/Kebyaord/Keyboard Shortcuts
3. Reset the shortcut to for start dock applications gsettings set org.gnome.shell.keybindings switch-to-application-3 "['<Ctrl><Alt>T']"

Method 2 (Xorg only) - Reset gnome default terminal

1. Create a script at ~/bin/single_gnome_terminal.sh

#!/bin/sh
SERVICE='gnome-terminal'

if ps ax | grep -v grep | grep $SERVICE > /dev/null
then
  wmctrl -xa $SERVICE
else
  $SERVICE
fi

2. Enable execution permission

chmod +x ~/bin/single_gnome_terminal.sh`

3. Install wmctrl

sudo apt-get install wmctrl

4. Change default terminal

gsettings set org.gnome.desktop.default-applications.terminal exec single_gnome_terminal.sh

References:

1. https://askubuntu.com/a/1194659
2. https://askubuntu.com/a/87109
3. https://unix.stackexchange.com/a/510376