Unknown, or unavailable dependency for gespeaker, needing python!

Ok, so you are trying to use GeSpeaker from Ubuntu 18.04 LTS repository. This previous Ubuntu version had more Python 2 libraries. You still can get them installed on 20.04 LTS by manual downloading:

cd ~/Downloads
wget -c http://archive.ubuntu.com/ubuntu/pool/universe/g/gespeaker/gespeaker_0.8.6-1_all.deb
wget -c http://archive.ubuntu.com/ubuntu/pool/universe/p/pygtk/python-glade2_2.24.0-5.1ubuntu2_amd64.deb
wget -c http://archive.ubuntu.com/ubuntu/pool/universe/p/pygtk/python-gtk2_2.24.0-5.1ubuntu2_amd64.deb
wget -c http://archive.ubuntu.com/ubuntu/pool/main/d/dbus-python/python-dbus_1.2.6-1_amd64.deb

sudo apt-get install ./gespeaker_0.8.6-1_all.deb ./python-glade2_2.24.0-5.1ubuntu2_amd64.deb ./python-gtk2_2.24.0-5.1ubuntu2_amd64.deb ./python-dbus_1.2.6-1_amd64.deb

and enjoy.