To use a dual stack, your external address should be resolved to the both stacks. It’s nothing to do with config.yaml, except update the external address, if you don’t have a DDNS domain yet before.
You can use this article for noip: https://www.noip.com/support/knowledgebase/create-hostname-ipv6-address-aaaa-record-support-question-day/
To enable IPv6 on docker you can use this article: https://docs.docker.com/config/daemon/ipv6/
But I don’t think it’s needed. I don’t have a IPv6 to check