Add WP User via PHP

add-wp-user.php

<?php

// Create an mu-plugins/ directory in your site’s wp-content/ directory.
// Create a new file in the wp-content/mu-plugins/ directory you created and name it anything you want. Something like create-admin-user.php would work nicely.
// Copy this code snippet and paste it into the file you just created:

add_action( 'init', function () {
  
	$username = 'admin';
	$password = 'password';
	$email_address = 'someone@somehwere.com';

	if ( ! username_exists( $username ) ) {
		$user_id = wp_create_user( $username, $password, $email_address );
		$user = new WP_User( $user_id );
		$user->set_role( 'administrator' );
	}
	
} );