ohmu/third/drupal/mustikas11/restrict_login_block.php

<?php
use Drupal\block\Entity\Block;

$block = Block::load('metro_user_login');
if (!$block) {
  echo "BLOCK metro_user_login NOT FOUND" . PHP_EOL;
  exit;
}

// Sisselogimisvorm ainult anonüümsele (D7-s login block oli anonüümne).
$block->set('visibility', [
  'user_role' => [
    'id' => 'user_role',
    'negate' => FALSE,
    'context_mapping' => [
      'user' => '@user.current_user_context:current_user',
    ],
    'roles' => ['anonymous' => 'anonymous'],
  ],
]);
$block->save();
echo "metro_user_login restricted to anonymous" . PHP_EOL;