Kartoza Geoserver on Heroku - docker

Question

I am new to docker and not an IT-specialist. I try to install Kartoza Geoserver in Docker on Heroku, but so far no success. Does anyone has experience with this and can explain me the settings in the dockerfile and the steps specifically for a Heroku install?
So far I tried a build with a modified dockerfile but I always get the same error (in the log trail) when opening/launching geoserver on Heroku:
"Error: groupadd: cannot open /etc/group".
I guess it is an permission/privileges issue.
Any sharing of experience on modifying the docker file so that the image is read by Heroku would be helpfull.
Modifying the settings in the dockerfile:
Removed the port forwarding from dockerfile
Add RUN adduser -D myuser USER myuser to dockerfile
Result dockerfile:
#--------- Generic stuff all our Dockerfiles should start with so we get caching ------------
ARG IMAGE_VERSION=9.0.65-jdk11-openjdk-slim-buster
ARG JAVA_HOME=/usr/local/openjdk-11
FROM tomcat:$IMAGE_VERSION
LABEL maintainer="Tim Sutton<tim#linfiniti.com>"
ARG GS_VERSION=2.22.0
ARG WAR_URL=https://downloads.sourceforge.net/project/geoserver/GeoServer/${GS_VERSION}/geoserver-${GS_VERSION}-war.zip
ARG STABLE_PLUGIN_BASE_URL=https://sourceforge.net/projects/geoserver/files/GeoServer
ARG DOWNLOAD_ALL_STABLE_EXTENSIONS=1
ARG DOWNLOAD_ALL_COMMUNITY_EXTENSIONS=1
ARG HTTPS_PORT=8443
ENV DEBIAN_FRONTEND=noninteractive
#Install extra fonts to use with sld font markers
RUN adduser -D myuser
USER myuser
RUN set -eux; \
apt-get update; \
apt-get -y --no-install-recommends install \
locales gnupg2 wget ca-certificates rpl pwgen software-properties-common iputils-ping \
apt-transport-https curl gettext fonts-cantarell lmodern ttf-aenigma \
ttf-bitstream-vera ttf-sjfonts tv-fonts libapr1-dev libssl-dev \
wget zip unzip curl xsltproc certbot cabextract gettext postgresql-client figlet gosu gdal-bin; \
# Install gdal3 - bullseye doesn't build libgdal-java anymore so we can't upgrade
curl https://deb.meteo.guru/velivole-keyring.asc | apt-key add - \
&& echo "deb https://deb.meteo.guru/debian buster main" > /etc/apt/sources.list.d/meteo.guru.list \
&& apt-get update \
&& apt-get -y --no-install-recommends install gdal-bin libgdal-java; \
dpkg-divert --local --rename --add /sbin/initctl \
&& (echo "Yes, do as I say!" | apt-get remove --force-yes login) \
&& apt-get clean \
&& rm -rf /var/lib/apt/lists/*; \
# verify that the binary works
gosu nobody true
ENV \
JAVA_HOME=${JAVA_HOME} \
DEBIAN_FRONTEND=noninteractive \
GEOSERVER_DATA_DIR=/opt/geoserver/data_dir \
GDAL_DATA=/usr/share/gdal \
LD_LIBRARY_PATH="$LD_LIBRARY_PATH:/usr/local/tomcat/native-jni-lib:/usr/lib/jni:/usr/local/apr/lib:/opt/libjpeg-turbo/lib64:/usr/lib:/usr/lib/x86_64-linux-gnu" \
FOOTPRINTS_DATA_DIR=/opt/footprints_dir \
GEOWEBCACHE_CACHE_DIR=/opt/geoserver/data_dir/gwc \
CERT_DIR=/etc/certs \
RANDFILE=/etc/certs/.rnd \
FONTS_DIR=/opt/fonts \
GEOSERVER_HOME=/geoserver \
EXTRA_CONFIG_DIR=/settings \
COMMUNITY_PLUGINS_DIR=/community_plugins \
STABLE_PLUGINS_DIR=/stable_plugins
WORKDIR /scripts
ADD resources /tmp/resources
ADD build_data /build_data
ADD scripts /scripts
RUN echo $GS_VERSION > /scripts/geoserver_version.txt ;\
chmod +x /scripts/*.sh;/scripts/setup.sh \
&& apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
RUN echo 'figlet -t "Kartoza Docker GeoServer"' >> ~/.bashrc
WORKDIR ${GEOSERVER_HOME}
ENTRYPOINT ["/bin/bash", "/scripts/entrypoint.sh"]
Then build it with argument --platform linux/amd64 (I use arm64 architecture). Then pushed it to Heroku. All the time I get the same error.