mysql_secure_installation: command not found

You have just installed MariaDB and as usual want to perform initial configuration by running mysql_secure_installation script but the error is:

mariadb_secure_installation: command not found

For MariaDB set ups you should use the following:

as starting rom MariaDB 10.4.6, mariadb-secure-installation is a symlink to mysql_secure_installation.
From MariaDB 10.5.2, mysql_secure_installation is the symlink, and mariadb-secure-installation is the binary name.
Good luck!