Creating user programmatically fails with Postgres

Anyone know what's wrong here? After the D8->D9 upgrade, a stupidly simple piece of code is not working, has there been a change? It worked before.

$params = [
  'name' => $username,
  'pass' => $password,
  'mail' => $email,
  'init' => $email,
];

$user = $this->users->create($params);

$user->enforceIsNew();
$user->save();

In D8 this was fine, in D9 I'm getting:

Drupal\Core\Entity\EntityStorageException: SQLSTATE[23502]: Not null violation: 7 ERROR:  null value in column "uid" of relation "drupal_users" violates not-null constraint
DETAIL:  Failing row contains (null, 740f7084-de66-4572-8ec7-049376cf5a33, en).: INSERT INTO "drupal_users" ("uuid", "langcode") VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1);

Research tells me that there was a change from D8 to D9.5 where the UID field is now a serial field instead of an integer using the sequence API.

In Postgres, you either omit the serial field, or use "DEFAULT".

The UID field is not being omitted but it's set to NULL. If I try to force it to be DEFAULT it gets type-cast to 0 (zero) and we get the UID already exists error.

How on earth can I create this user programmatically?

It turned out that there was a database update that hadn't been run on the test site, the one that switched the users.UID column to being serial, instead of int.

Instead of explicitly setting the "uid" value in your code, you can let the database handle it by omitting it from the $params array.