Since Ubuntu 20.04 used in this guide only has MySQL 8.0 in the APT repository. So download MySQL 5.7 APT Repository and install MySQL server and client. wget https ...
apt-get purge mysql-community-c* mysql-server-8.0 apt-get purge mysql-community-server sudo rm -rf /etc/mysql /var/lib/mysql /var/log/mysql sudo dpkg --purge mysql ...