Issue #3266600 by Gábor Hojtsy, Liam Morland: Check that D9 version is at...

    ];

    if ($this->nextMajor == 10) {

      // @todo update this as the situation develops.

      $build['description'] = $this->t('<a href=":environment">Drupal 10 environment requirements are still evolving</a>. Upgrades to Drupal 10 are planned to be supported from Drupal 9.3.x and Drupal 9.4.x.', [':environment' => 'https://www.drupal.org/project/drupal/issues/3118147']);

      $build['description'] = $this->t('Upgrades to Drupal 10 are supported from Drupal 9.3.x and Drupal 9.4.x. It is suggested to update to the latest Drupal 9 version available. <a href=":platform">Several hosting platform requirements have been raised for Drupal 10</a>.', [':platform' => 'https://www.drupal.org/node/3228686']);

      // Check Drupal version. Link to update if available.

      $core_version_info = [

        '#type' => 'markup',

        '#markup' => $this->t('Version @version.', ['@version' => \Drupal::VERSION]),

      ];

      $has_core_update = FALSE;

      $core_update_info = $this->releaseStore->get('drupal');

      if (isset($core_update_info['releases']) && is_array($core_update_info['releases'])) {

        // Find the latest release that are higher than our current and is not beta/alpha/rc.

        foreach ($core_update_info['releases'] as $version => $release) {

          $major_version = explode('.', $version)[0];

          if ((version_compare($version, \Drupal::VERSION) > 0) && empty($release['version_extra']) && $major_version === '9') {

            $link = $core_update_info['link'] . '/releases/' . $version;

            $core_version_info = [

              '#type' => 'link',

              '#title' => version_compare(\Drupal::VERSION, '9.3.0') >= 0 ?

                $this->t('Version @current allows to upgrade but @new is available.', ['@current' => \Drupal::VERSION, '@new' => $version]) :

                $this->t('Version @current does not allow to upgrade and @new is available.', ['@current' => \Drupal::VERSION, '@new' => $version]),

              '#url' => Url::fromUri($link),

            ];

            $has_core_update = TRUE;

            break;

          }

        }

      }

      if (version_compare(\Drupal::VERSION, '9.3.0') >= 0) {

        if (!$has_core_update) {

          $class = 'no-known-error';

        }

        else {

          $class = 'known-warning';

        }

      }

      else {

        $status = FALSE;

        $class = 'known-error';

      }

      $build['data']['#rows'][] = [

        'class' => $class,

        'data' => [

          'requirement' => [

            'class' => 'requirement-label',

            'data' => $this->t('Drupal core should be at least 9.3.x'),

          ],

          'status' => [

            'data' => $core_version_info,

            'class' => 'status-info',

          ],

        ]

      ];

      // Check PHP version.

      $version = PHP_VERSION;

    // Check Drupal version. Link to update if available.

    $core_version_info = [

      '#type' => 'markup',

      '#markup' => $this->t('Version @version and up to date.', ['@version' => \Drupal::VERSION]),

      '#markup' => $this->t('Version @version.', ['@version' => \Drupal::VERSION]),

    ];

    $has_core_update = FALSE;

    $core_update_info = $this->releaseStore->get('drupal');

          $link = $core_update_info['link'] . '/releases/' . $version;

          $core_version_info = [

            '#type' => 'link',

            '#title' => $this->t('Version @current allows to upgrade but @new is available.', ['@current' => \Drupal::VERSION, '@new' => $version]),

            '#title' => version_compare(\Drupal::VERSION, '8.8.0') >= 0 ?

              $this->t('Version @current allows to upgrade but @new is available.', ['@current' => \Drupal::VERSION, '@new' => $version]) :

              $this->t('Version @current does not allow to upgrade and @new is available.', ['@current' => \Drupal::VERSION, '@new' => $version]),

            '#url' => Url::fromUri($link),

          ];

          $has_core_update = TRUE;