Since Drupal VM is built in a modular fashion, and the upstream Ansible Role that installs and configures MySQL is built in a way that works with any MySQL-compatible replacement, you can easily swap out MySQL for MariaDB.
The simplest way is to add the following lines after the
# MySQL Configuration. line in
mysql_packages: - mariadb-client - mariadb-server - python-mysqldb
This set of packages works out of the box with Ubuntu 18.04 installation that comes with Drupal VM.
Alternatively, if you want to use RedHat 8 or CentOS 8 instead of Ubuntu, you can set the following variables to install and configure MariaDB instead of MySQL:
mysql_packages: - mariadb - mariadb-server - mariadb-libs - MySQL-python - perl-DBD-MySQL mysql_daemon: mariadb mysql_socket: /var/lib/mysql/mysql.sock mysql_log_error: /var/log/mariadb/mariadb.log mysql_syslog_tag: mariadb mysql_pid_file: /var/run/mariadb/mariadb.pid