Usually you’ll want to check at the cloud-init log files in /var/log and also check /var/lib/cloud/seed to confirm the right YAML made it in.
Note that cloud-init is only templated on creation, so changing the profile and restarting the container won’t work, you need to create a new container or use this workaround:
- lxc config set NAME volatile.apply_template create
- lxc start NAME