Upgrading from Drupal 7 to Drupal 10

Create a new D10 portal. Enable migrate modules.

Enable https://www.drupal.org/project/migrate_upgrade to allow migrations via Drush.

Set up a Migrate Database

$databases['migrate']['default'] = [
  'database' => 'drupal7db',
  'username' => 'drupal7db',
  'password' => 'drupal7db',
  'prefix' => '',
  'host' => 'localhost',
  'port' => '',
  'driver' => 'mysql',
  'namespace' => 'Drupal\\mysql\\Driver\\Database\\mysql',
  'autoload' => 'core/modules/mysql/src/Driver/Database/mysql/',
];

Migrate configurations only via Drush

drush migrate:upgrade --legacy-db-key=migrate --legacy-root=https://example.com --configure-only

Creating a new custom field. Ex: og_group_ref. Drush provides intuitive interface to create a field with custom machine name

drush field:create

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Links
https://www.drupal.org/docs/upgrading-drupal/upgrading-from-drupal-6-or-...
https://www.drupal.org/docs/upgrading-drupal/upgrading-from-drupal-6-or-...
https://www.drupal.org/docs/upgrading-drupal/upgrading-from-drupal-6-or-...

https://www.drupal.org/docs/contributed-modules/create-fields-programmat...