I'm not sure if this is related or not; but recently composer updated his version and it's not compatible with magento latest version.
Basicaly, in my docker I had to change
curl -sS https://getcomposer.org/installer | php -- --filename=composer --install-dir=/usr/local/bin \
curl -sS 'https://getcomposer.org/installer' | php -- --version=1.10.16 --...
Did you check if composer is installed and configured correctly. What happens when you run composer --version? If its installed, check to see if its enabled globally. Go over the steps from https://getcomposer.org/doc/00-intro.md and try again. One more thing, did you install Magento via composer or dowloaded it as a zip ?
No, It is not possible currently to log in as an admin using CLI in Magento 2 but you can create a new user like:
php bin/magento admin:user:create --admin-user=mageuser --admin-password=HiMagento123 --email@example.com --admin-firstname=John --admin-lastname=Doe
Or you can check the below command for more details:
php bin/magento admin:user:...