Normally, when creating Tweets from Drupal 8 I use the Social Post Twitter module. This module is part of the Drupal Social Initiative and has been my go-to module when I've needed to read or send Tweets from a Drupal site. Since the release of Drupal 9, however, these modules have not been receiving the support needed and as of writing this article there is no easy way to install them on a Drupal 9 site. I've looked into the issue queues and can't see why the delay is there.
The Social Post Twitter module does have a lot of features that I didn't need for what I was looking for, which was to send Tweets when items of content are created. I decided to see how difficult it would be to send Tweets from a Drupal site as an item of content is published.