c.isArray is not a function

Exactly the same problem here.

I think it's related to JQuery version. Drupal 11 ships jQuery 4.0, and isArray is a function deprecated on it. I think Select2 has not jQuery 4 support: https://github.com/select2/select2/issues/6298

I have the same problem in Drupal 11.1.6, I have solved it by changing the dependency
composer require npm-asset/select2:4.1.0-rc.0