Migrated a Drupal 8 site to another server running apache2 PHP 5.5.9 (should be supported). Apache returns 500 when index.php requested, but no errors are logged anywhere. I tested by forcing an intentional PHP error in index.php and the log contains PHP errors.
I also excluded database connection problems. Taking settings.php out redirects me correctly to /core/install.php and no error is thrown.