create mysql user
sudo mysql --user=root mysql
2. Create a user for phpMyAdmin
Run the following commands (replacing some_pass by the desired password):
CREATE USER 'phpmyadmin'@'localhost' IDENTIFIED BY 'some_pass';
GRANT ALL PRIVILEGES ON *.* TO 'phpmyadmin'@'localhost' WITH GRANT OPTION;
FLUSH PRIVILEGES;
CREDITS: [link](https://askubuntu.com/questions/763336/cannot-enter-phpmyadmin-as-root-mysql-5-7/763359#763359)