The MySQL flavoured LEMP stack still installs MariaDB. Is there a way to NOT install this garbage?
In both Jessie and Stretch there is also a mariadb-server package which is a MariaDB-specific analog to the mysql-server package. In Jessie this package depends on mariadb-server-10.0 and in Stretch this package depends on mariadb-server-10.1 (the same as the default-mysql-server package).
So, the main repository difference in Debian 9 “Stretch” is that when you install the mysql-server package on Stretch you will get MariaDB 10.1 instead of MySQL, like you would with previous versions of Debian. Note that mysql-server is just an empty transitional meta-package and users are encouraged to install MariaDB using the actual package mariadb-server.
Update: This is a work around to NOT install maria-db:
# echo -e "deb http://repo.mysql.com/apt/d... stretch mysql-5.7\ndeb-src http://repo.mysql.com/apt/d... stretch mysql-5.7" > /etc/apt/sources.list.d/mysql.list
# wget -O /tmp/RPM-GPG-KEY-mysql https://repo.mysql.com/RPM-...
# apt-key add /tmp/RPM-GPG-KEY-mysql
# apt update
# apt install mysql-server