According the help of ansible-playbook one could use
--user=REMOTE_USER to define the ssh user, but one could also define
ansible_ssh_user: REMOTE_USER in either the host- or group_vars.
What variable need to be defined in either the group- or host_vars directory to prevent that
--vault-password-file has to be defined while running
ansible_vault_password_file: ~/.vault_pass.txtis defined in the config the decryption fails:
ERROR! Decryption failed on /path/to/vault
No associated vault variables was found in this documentation