Docker Error standard_init_linux.go:185: exec user process caused "exec format error with Qnap TS131P

My Docker file is song/songkong at https://hub.docker.com/r/songkong/songkong/~/dockerfile/

FROM openjdk:8-jre-alpine

RUN apk --no-cache add \
      ca-certificates \
      curl \
      fontconfig \
      msttcorefonts-installer \
      tini \
 && update-ms-fonts \
 && fc-cache -f

RUN mkdir -p /opt \
 && curl http://www.jthink.net/songkong/downloads/current/songkong-linux-headless-novm.tgz?val=77 | tar -C /opt -xzf - \
&& find /opt/songkong -perm /u+x -type f -print0 | xargs -0 chmod a+x

RUN addgroup -S songkong \
 && adduser -S -G songkong songkong

USER songkong:songkong

EXPOSE 4567

ENTRYPOINT ["/sbin/tini"]

# Config, License, Logs, Reports and Internal Database
VOLUME /songkong

# Music folder should be mounted here
VOLUME /music

WORKDIR /opt/songkong

CMD /opt/songkong/songkongremote8.sh

it works fine with a Synology DS218+ Disk Station (Intel)

I purchased a Qnap TS-131P to test with Qnap, but also to confirm it works with Arm processor, since Qnap supports Docker on arm processors whereas Synology does not.

When I try to start Container from the image I get an error

standard_init_linux.go:185: exec user process caused "exec format error 

and this link makes me think the problem is due to the arm processor.

But I am confused since I thought the whole point of Docker was to hide these system specific details away, how (can I) fix my Docker File so it works on Qnap.