Looks like there is a new build user in town for bullseye

Dockerfile-bullseye

 FROM debian:bullseye
 RUN apt-get update && apt-get -y upgrade
 RUN apt-get install -y git curl build-essential debhelper dh-autoreconf autotools-dev libssl-dev nettle-dev docbook2x lsb-release
-WORKDIR /root/
+WORKDIR /tmp/
 COPY build.sh build.sh
 RUN ./build.sh
 CMD tar c *.deb