If your docker container hangs, or complains that no display is available, even though you have an xvfb-run entrypoint, you probably need a custom init handler:
# use custom init handler so that xvfb-run is executed properly
# alternatively use docker --init, but that doesnt work in k8s
ENV TINI_VERSION v0.19.0
ADD https://github.com/krallin/tini/releases/download/${TINI_VERSION}/tini /tini
RUN chmod +x /tini