Drupal default git clone command not working

It may help to execute the command in debug mode and let us know.

As far as I’m aware, there is not a general problem with git.drupalcode.org, this is likely an issue with your internet connection, ISP, or other local issue.

More debugging, as cilefen mentioned, is needed. Especially GIT_CURL_VERBOSE=1 since this looks like a curl-related error.

Do you have any proxies, VPNs, firewalls, that might be interfering?