Shutter is removed from the main Ubuntu repositories since Ubuntu 18.10, along with some old Gnome libraries required by the screenshot tool. It is however can be easily installed via the community maintained PPA repository in Ubuntu 19.10, Ubuntu 20.04.
How to Install Shutter in Ubuntu 20.04:
1. Open terminal by either pressing Ctrl+Alt+T on keyboard or searching for ‘terminal’ from application menu. When it opens, run command to add the PPA:
sudo add-apt-repository ppa:linuxuprising/shutter
Type user password (no asterisk feedback) when it asks and hit Enter to continue.
2. Then install the screenshot tool via command:
sudo apt install shutter
For Ubuntu derivatives, you may need to run sudo apt update first to refresh system package cache.
To remove Shutter screenshot tool, open terminal and run command:
sudo apt remove --autoremove shutter
To remove the PPA, launch Software & Updates and navigate to Other Software tab, then the repository line.