Installing MariaDB 10.4 on OpenBSD 6.7 is almost the same to MariaDB 10.0 on OpenBSD 6.4:
There is, however, a significant difference: "The unix_socket authentication plugin is now default on Unix-like systems" since MariaDB 10.4.
The steps to install it is as below.
First, install the package and prepare the daemon:
$ doas pkg_add mariadb-server
pkg-readme is created as
Create a default database first:
$ doas rcctl enable mysqld $ doas mysql_install_db $ doas rcctl start mysqld
$ doas mysql_secure_installation
You'll be asked whether to use the unix_socket authentication or not, after the first confirmation "Enter current password for root (enter for none):".
The steps followed by it were as usual; such as whether to set root password, remove anonymous users, disallow root login remotely and remove test database.
That'll be it.