This is an updated version of a previously archived repository base Alpine image with the S6 Overlay.
You probably don't want to run this directly, you probably want to build it so you can then build and run ddns.
Build:
docker buildx build --tag djf/alpine-s6 -f Dockerfile --platform linux/arm64 .
If you really want to run it (testing?), do:
docker run djf/alpine-s6
See the S6 Overlay Documentation for details on how to manage services.