Install and enable pwa modules on magento 2.4.4 in order to use it as backend server of pwa-studio project i.e MAGENTO_BACKEND_URL
cd magento_root_dir
mkdir ext
git clone https://github.com/magento/magento2-pwa.git ext/magento/magento2-pwa
composer config minimum-stability dev
composer config repositories.ext path "./ext/*/*/*"
composer require magento/pwa