Para a instalação do do Cisco Packet Tracer 7.3 no Ubuntu 18.04, Ubuntu 20.04 ou Mint 19, baixe os pacotes .deb como nos links sugeridos a seguir:

wget https://archive.org/download/packettracer730mac_202002/PacketTracer_730_amd64.deb
wget http://ftp.br.debian.org/debian/pool/main/d/double-conversion/libdouble-conversion1_3.1.0-3_amd64.deb
wget http://archive.ubuntu.com/ubuntu/pool/main/libj/libjpeg-turbo/libjpeg-turbo8_2.0.3-0ubuntu1_amd64.deb
wget http://archive.ubuntu.com/ubuntu/pool/main/libj/libjpeg8-empty/libjpeg8_8c-2ubuntu8_amd64.deb

Logo depois, caso necessário, autorize o modo de execução (com o comando chmod) e instale os pacotes:

sudo chmod +x libdouble-conversion1_3.1.0-3_amd64.deb libjpeg-turbo8_2.0.3-0ubuntu1_amd64.deb libjpeg8_8c-2ubuntu8_amd64.deb PacketTracer_730_amd64.deb
sudo dpkg -i libdouble-conversion1_3.1.0-3_amd64.deb libjpeg-turbo8_2.0.3-0ubuntu1_amd64.deb libjpeg8_8c-2ubuntu8_amd64.deb PacketTracer_730_amd64.deb

A seguir, edite o arquivo /var/lib/dpkg/status e delete ou comente a linha:

"depends: libdouble-conversion1, qt-at-spi"

Caso necessário, execute:

sudo apt --fix-broken install