In step 2 you could create a config.php manually and set the database and url properties there, see:
<?php return [
'debug' => false,
'offline' => false,
'database' =>
[
'driver' => 'mysql',
'host' => 'localhost',
'database' => 'flarum',
'username' => 'root',
'password' => '',
'charset' => 'utf8mb4',
'collation' => 'utf8mb4_unicode_ci',
'prefix' => '',
'port' => '3306',
'strict' => false,
],
'url' => 'http://flarum.test',
];
