Hi Luigi,
Welcome to BuddyDev.

Please define simple users. Is it users with ‘subscriber’ role?

Thank you
Brajesh

Please use the following

/**
 * Check if a user has given WordPress role(or any of the roles).
 *
 * @param int           $user_id user.
 * @param string|array  $role role(s).
 *
 * @return bool|array
 */
function buddydev_user_has_role( $user_id, $role ) {
	$user   = get_user_by( 'id', $user_id );

	if ( empty( $user ) ) {
		return false;
	}

	$user_roles = $user->roles;

	if ( empty( $user_roles ) ) {
		return false;
	}
	// if an array o roles was given.
	return is_array( $role) ? array_intersect( $role, $user_roles ) : in_array( $role, $user_roles, true );
}

/**
 * Only allow galleries for a certain role.
 *
 * @param bool   $is_active Can create gallery or not.
 * @param string $component Component name.
 * @param int    $component_id Component id.
 *
 * @return bool
 */
function buddydev_disable_gallery_for_roles( $is_active, $component, $component_id ) {

	if ( 'members' !== $component ) {
		return $is_active;
	}

	$restricted_roles = array( 'subscriber', 'contributor' );// 'editor', 'contributor', 'subscriber'

	if ( buddydev_user_has_role( $component_id, $restricted_roles ) ) {
		$is_active = false;
	}

	return $is_active;
}
add_filter( 'mpp_is_enabled', 'buddydev_disable_gallery_for_roles', 10, 3 );

Please feel free to modify the roles list.

Let me know if it works for you or not?

PS:- The code should go to wp-content/plugins/bp-custom.php

Regards
Brajesh

Hi Luigi,
Thank you.
If it is not there, Please create a php file. You can use the following(start with php tag)
https://gist.github.com/sbrajesh/55639df69806b564a9765562a4f40e37

as the starting template. Also, Please make sure to remove the code from class-buddypress.php, It should not be modified as the next update of BuddyPress will overwrite it.

Regards
Brajesh