If you want to use this docker image, you should use ghcr.io/daniel-marynicz/keycloak:<VERSION>
or ghcr.io/daniel-marynicz/keycloak:<VERSION>-alpine
as the base image.
For further more information, please see the Running Keycloak in a container guide.
If you need to build it yourself, you can do it like this
VERSION=<VERSION> TAG="<YOUR_TAG>:${VERSION}" docker buildx bake