This is a docker container that implements unbound on the local host. By default, it listens for queries on 127.0.0.1#3535 so you can run it on your pihole host and have it as the upstream server. Unbound will traverse authoritative nameservers to find the answer to queries, as well as maintain a cache.
I chose port 3535 because 5353 would be preferred but it conflicts with Avahi on the docker host and I still want that to run.
This is not multi-arch. It only works on arm32v6 currently. You can change this by downloading from the repo and changing the FROM reference to simply alpine:latest and building locally
One-off: docker run -d -p 3535:3535/udp airbornelamb/pihole-unbound and then input 127.0.0.1#3535 as your pihole upstream DNS provider
In a swarm stack: Checkout my full pihole and unbound stack here https://raw.githubusercontent.com/airbornelamb/rpi/master/pihole-stack.yml