To uninstall jack-keyboard just follow these instructions.
sudo apt-get remove jack-keyboard
This will remove just the jack-keyboard package itself.
sudo apt-get remove --auto-remove jack-keyboard
This will remove the jack-keyboard package and any other dependant packages which are no longer needed.
If you also want to delete your local/config files for jack-keyboard then this will work.
sudo apt-get purge jack-keyboard
Or similarly, like this jack-keyboard
sudo apt-get purge --auto-remove jack-keyboard
|Maintainer||Debian Multimedia Maintainers <firstname.lastname@example.org>|
|Description||Virtual MIDI keyboard for JACK MIDI|