docker-magento: bin/download fails, unable to create config.json Permission Denied

Description Brand new Linux VM, Debian 10, with Docker + Docker-Compose.

Tried entering curl -s https://raw.githubusercontent.com/markshust/docker-magento/master/lib/onelinesetup | bash -s -- magento.test 2.4.2

Failed with below.

Following https://github.com/markshust/docker-magento/blob/master/SETUP.md

Upon entering bin/download 2.3.4

Starting magento_elasticsearch_1 ... done
Starting magento_redis_1         ... done
Starting magento_db_1            ... done
Starting magento_rabbitmq_1      ... done
Creating magento_phpfpm_1        ... done
Creating magento_app_1           ... done

Composer authentication required (repo.magento.com public and private keys):
    Username: <my public key>
    Password: <my private key>



  [ErrorException]
  touch(): Unable to create file /var/www/.composer/config.json because Permission denied


config [-g|--global] [-e|--editor] [-a|--auth] [--unset] [-l|--list] [-f|--file FILE] [--absolute] [--] [<setting-key>] [<setting-value>]...

Composer auth has been setup.
Cannot create cache directory /var/www/.composer/cache/repo/https---repo.packagist.org/, or directory is not writable. Proceeding without cache
Cannot create cache directory /var/www/.composer/cache/files/, or directory is not writable. Proceeding without cache
Cannot create cache directory /var/www/.composer/cache/repo/https---repo.magento.com/, or directory is not writable. Proceeding without cache
Creating a "magento/project-community-edition=2.3.4" project at "./"
Warning from repo.magento.com: You haven't provided your Magento authentication keys. For instructions, visit https://devdocs.magento.com/guides/v2.3/install-gde/prereq/connect-auth.html
Warning from repo.magento.com: You haven't provided your Magento authentication keys. For instructions, visit https://devdocs.magento.com/guides/v2.3/install-gde/prereq/connect-auth.html
Warning from repo.magento.com: You haven't provided your Magento authentication keys. For instructions, visit https://devdocs.magento.com/guides/v2.3/install-gde/prereq/connect-auth.html


  [Composer\Downloader\TransportException]
  The 'https://repo.magento.com/packages.json' URL required authentication.
  You must be using the interactive console to authenticate


create-project [-s|--stability STABILITY] [--prefer-source] [--prefer-dist] [--repository REPOSITORY] [--repository-url REPOSITORY-URL] [--add-repository] [--dev] [--no-dev] [--no-custom-installers] [--no-scripts] [--no-progress] [--no-secure-http] [--keep-vcs] [--remove-vcs] [--no-install] [--ignore-platform-reqs] [--] [<package>] [<directory>] [<version>]

Even tried creating /var/www/.composer/config.json and setting its perms to 777 (to test). Still fails.

Tried sudo bin/download 2.3.4 and it still fails. Tried it as root (last hope) and it fails.

Same result with bin/download and bin/download 2.3.0.

Steps To Reproduce See description.

Expected Result Successful install/setup

Actual Result Failed, see description