This CodeLet will display a block content in a region programmatically. You have to implement hook_preprocess_HOOK() in THEMENAME.theme file of your theme directory.
CodeLet
<?php/** * Implements hook_preprocess_HOOK() for HTML document templates. * * Add block in a region. */function THEMENAME_preprocess_html(&$variables) {$block = \Drupal\block\Entity\Block::load('YOUR_BLOCK_ID'); $block_content = \Drupal::entityManager() ->getViewBuilder('block') ->view($block); $variables['page']['YOUR REGION'][] = $block_content;}?>