One of our internal support engineers got it to work using the CircleCI base convenience image and then adding the kaniko binaries.
FROM cimg/base:current
ARG user=circleci
# Copy Needed Files from Kaniko Image
COPY --from=gcr.io/kaniko-project/executor --chown=$user /kaniko/executor /kaniko/executor
COPY --from=gcr.io/kaniko-project/executor --chown=$user /kaniko/docker-credential-gcr /kaniko/docker-credential-gcr
COPY --from=gcr.io/kaniko-project/executor --chown=$user /kaniko/docker-credential-ecr-login /kaniko/docker-credential-ecr-login
COPY --from=gcr.io/kaniko-project/executor --chown=$user /kaniko/docker-credential-acr-env /kaniko/docker-credential-acr-env
COPY --from=gcr.io/kaniko-project/executor --chown=$user /kaniko/.docker /kaniko/.docker
COPY --from=gcr.io/kaniko-project/executor --chown=$user /kaniko/ssl/certs /kaniko/ssl/certs/
COPY --from=gcr.io/kaniko-project/executor --chown=$user /etc/nsswitch.conf /etc/nsswitch.conf
# Setting Enviroment Variables for Kaniko
# ENV HOME /root
# ENV USER root
# FYI, ENV HOME and USER should not be set
ENV PATH="${PATH}:/kaniko"
ENV SSL_CERT_DIR=/kaniko/ssl/certs
ENV DOCKER_CONFIG /kaniko/.docker/
ENV DOCKER_CREDENTIAL_GCR_CONFIG /kaniko/.config/gcloud/docker_credential_gcr_config.json
could you try that?