How to check and change default front page programmatically in Drupal 8 & 9
To get current front page value:
$frontPage = \Drupal::configFactory()->get('system.site')->get('page.front');
To check if current page is the front page:
$isFront = \Drupal::service('path.matcher')->isFrontPage();
To change the front page to a new path:
\Drupal::configFactory()->getEditable('system.site')->set('page.front', '/dashboard')->save();
