Problem:

Change directory to Drupal 8/9 instance, and run composer require drupal/console 

Then, this error occur:

Solution:

Install 2 missing modules by running the below composer commands:

composer require symfony/filesystem:"4.4.8 as 3.4.35"


composer require symfony/finder:"4.4.8 as 3.4.35"

Then run the composer require drupal/console  again.