The error is:
InvalidPrivsError: unable to parse the MySQL grant string: GRANT USAGE ON entrypoint.sh TO `wallabag`@`%` IDENTIFIED BY PASSWORD '[OMMITED]'
Which appears to be related to ansible/ansible#51356. Simply upgrading ansible inside the container solves the issue:
apk add py3-pip
pip3 install --upgrade ansible
And then the provisioner can be run again:
ansible-playbook -i /etc/ansible/hosts /etc/ansible/entrypoint.yml -c local
This error avoided the container from starting properly and the logs where showing HTTP 500 error codes.