mysql-server-5.7 is not configured yet

Ok, I solved in this way:

• I used Software & Updates application to remove mariadb sources
• executed the followings steps (ref https://askubuntu.com/a/934576):
• sudo apt purge mysql-client-5.7 mysql-client-core-5.7 mysql-common mysql-server-5.7 mysql-server-core-5.7 mysql-server
• sudo apt update && sudo apt dist-upgrade && sudo apt autoremove && sudo apt -f install
• sudo apt install mysql-server

This fixed it for me (MySQL 8.0 - Ubuntu 20.04)

sudo apt-get purge mysql\* libmysql\*
sudo apt autoremove

But the package "mysql-client-core-8.0" don't uninstall, so...

sudo apt --fix-broken install
sudo apt-get --reinstall install mysql-client-core-8.0
sudo apt-get purge mysql\* libmysql\*
sudo apt autoremove
sudo apt update
sudo apt install mysql-server

No more errors!