Updating from 1.x to 2.0.1@alpha purges settings and grant field data

nodeaccess.settings.yml 1.x

grants:
  view: 1
  edit: 1
  delete: 1
priority: 0
preserve: 1

nodeaccess.settings.yml 2.x

allowed_grant_operations:
  grant_view: true
  grant_update: true
  grant_delete: true
bundles_roles_grants: {}
grants_tab_availability: {}
map_rid_gid: {}
roles_settings: {}

There is an update hook provided in nodeaccess.install:
https://git.drupalcode.org/project/nodeaccess/-/blob/2.0.x/nodeaccess.in...

/**
 * Migrates nodeaccess.settings.
 */
function nodeaccess_update_9002(&$sandbox) {
  $config = \Drupal::configFactory()->getEditable('nodeaccess.settings');
  // From grants to allowed_grant_operations.
  $old_grants = $config->get('grants');
  $config
    ->set('allowed_grant_operations', [
      'grant_view' => (boolean) $old_grants['view'],
      'grant_update' => (boolean) $old_grants['edit'],
      'grant_delete' => (boolean) $old_grants['delete'],
    ])
    ->clear('grants');

  // From allowed_types to grants_tab_availability.
  $old_allowed_types = $config->get('allowed_types') ?? [];
  $grants_tab_availability = [];
  foreach ($old_allowed_types as $bundle => $value) {
    $grants_tab_availability[$bundle] = (boolean) $value;
  }
  $config
    ->set('grants_tab_availability', $grants_tab_availability)
    ->clear('allowed_types');

  // From role_map to map_rid_gid.
  $old_role_map = $config->get('role_map');
  $config
    ->set('map_rid_gid', $old_role_map)
    ->clear('role_map');

  // From role_alias to roles_settings.
  $old_role_alias = $config->get('role_alias');
  $roles_settings = [];
  foreach ($old_role_alias as $role_id => $value) {
    $roles_settings[$role_id] = [
      'display_name' => $value['alias'],
      'name' => $value['name'],
      'weight' => (int) $value['weight'],
      'selected' => (boolean) $value['allow'],
    ];
  }
  $config
    ->set('roles_settings', $roles_settings)
    ->clear('role_alias');

  $bundles = array_keys($old_allowed_types);
  $bundles_roles_grants = [];
  foreach ($bundles as $bundle) {
    $old_bundle_settings = $config->get($bundle);
    foreach ($old_bundle_settings as $role_id => $grant) {
      $bundles_roles_grants[$bundle][$role_id] = [
        'grant_view' => (int) $grant['grant_view'],
        'grant_update' => (int) $grant['grant_update'],
        'grant_delete' => (int) $grant['grant_delete'],
      ];
    }
    $config->clear($bundle);
  }
  $config
    ->set('bundles_roles_grants', $bundles_roles_grants)
    ->clear('priority')
    ->clear('preserve')
    ->save();

}

Did you run drush updb / drush updatedb and drush cr / drush cache:rebuild?

Please let me know and I can investigate this further if you're still having issues?

Is this the same issue as:
https://www.drupal.org/project/nodeaccess/issues/3509391 💬 Upgrade to version 2 deletes existing permissions Active

If so we should also mark one of these as closed (duplicate).

The settings are successfully migrated with updb.
But the individual grants per user are deleted during update.