Shiny app (leafviz) in docker container not loading in browser - docker

Question

I am building a docker container to use the Leafcutter and Leafviz analysis tools. The final visualization commanded from an R file uses shiny app, it works fine on my machine but when ran in the container I can't connect to it.
I run the container with the following line of code:
docker run -dit --name leaf --rm -p 1234:1234 leafcutter
All is in order when I check with docker ps:
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
783f550df965 leafcutter "bash" 2 minutes ago Up 2 minutes 0.0.0.0:1234->1234/tcp, :::1234->1234/tcp leaf
Executing the pipeline in the container calls several snakefiles, and the last rule of the last one calls the R file:
Rscript /path/to/run_leafviz.R -i {input}
That script calls several functions before calling leafviz() which basically just runs the shiny app, I've modified the options like so:
shiny::runApp(launch.browser=FALSE, appDir = system.file("application", package = "leafviz"), host = "0.0.0.0", port = 1234)
All the shiny files and packages are installed with the R leafviz package. When I execute my container all goes fine, the output shows "Listening on http://0.0.0.0:1234", but when I try to connect I get the "connexion failed" page.
My Dockerfile is fairly large but here are the most relevant parts:
FROM ubuntu:22.04
ENV DEBIAN_FRONTEND noninteractive
#Install Ubuntu packages
RUN apt-get update && apt-get install \
-y cmake -y curl \
-y default-jre \
-y gdebi-core \
-y less -y libarchive13 -y libbz2-dev -y libcairo2-dev -y libcurl4-openssl-dev -y libgsl-dev \
-y liblzma-dev -y libncurses5-dev -y libncursesw5-dev -y libssl-dev -y libxml2-dev -y libxt-dev \
-y pandoc -y pandoc-citeproc -y python-pip \
-y tabix \
-y unzip \
-y wget \
-y zlib1g-dev \
&& rm -rf /var/lib/apt/lists/*
#Install conda, snakemake, samtools, regtools...
#[...]
#Install R
LABEL org.label-schema.license="GPL-2.0" \
org.label-schema.vcs-url="https://github.com/rocker-org/r-apt" \
org.label-schema.vendor="Rocker Project" \
maintainer="Dirk Eddelbuettel <edd#debian.org>"
RUN useradd docker \
&& mkdir /home/docker \
&& chown docker:docker /home/docker \
&& addgroup docker staff
RUN apt-get update \
&& apt-get install -y --no-install-recommends \
littler r-base r-base-dev r-recommended r-cran-docopt
RUN ln -s /usr/lib/R/site-library/littler/examples/install.r /usr/local/bin/install.r \
&& ln -s /usr/lib/R/site-library/littler/examples/install2.r /usr/local/bin/install2.r \
&& ln -s /usr/lib/R/site-library/littler/examples/installGithub.r /usr/local/bin/installGithub.r \
&& ln -s /usr/lib/R/site-library/littler/examples/testInstalled.r /usr/local/bin/testInstalled.r \
&& rm -rf /tmp/downloaded_packages/ /tmp/*.rds \
&& rm -rf /var/lib/apt/lists/*
#Install shiny server (I have tried with and without this RUN command)
RUN wget --no-verbose https://s3.amazonaws.com/rstudio-shiny-server-os-build/ubuntu-12.04/x86_64/VERSION -O "version.txt" && \
VERSION=$(cat version.txt) && \
wget --no-verbose "https://s3.amazonaws.com/rstudio-shiny-server-os-build/ubuntu-12.04/x86_64/shiny-server-$VERSION-amd64.deb" -O ss-latest.deb && \
gdebi -n ss-latest.deb && \
rm -f version.txt ss-latest.deb
EXPOSE 1234
#Install R packages
COPY install_packages.R /tmp/install_packages.R
RUN Rscript /tmp/install_packages.R
CMD ["bash"]
I've been learning docker quite chaotically so I don't know if some elements are clashing, but I have exposed the container port and published it to the host and no error message seems to indicate there is a problem coming from somewhere else. I would really appreciate some help.