I have now installed amasty extension on Bitnami Cloud hosts Magento stacks in version 2.4.1-8 and everything went well.
I proceeded as follows:
sudo chown -R bitnami: daemon/opt/bitnami/magento/
composer config repositories.amasty composer https://composer.amasty.com/community/
composer require amasty/module-mass-order-actions
sudo bin/magento-cli setup: upgrade
sudo chown -R daemon: daemon/opt/bitnami/magento/
sudo bin/magento-cli cache: flush
I have the auth.jsom file in: /home/bitnami/.config/composer (owner/group is: bitnami/bitnami)
Try it, maybe it will help.