Download D7 module using Composer for D8? I'm using Drush 10, and I can't use dl to download a module, since the command was removed to push Composer use. Is there a way for me to download a Drupal 7 module into a Drupal 8 site using Composer, so that I can use Drupal 7 to 8/9 Module Upgrader on it?

The project I want to download doesn't have a D8 version yet, and it has no composer.json.
If I were you, I would just use wget.

Copy the Zip file url, ex:

sudo wget https://ftp.drupal.org/files/projects/views-7.x-3.24.zip


and then

sudo unzip views-7.x-3.24.zip