inside image: "Address not available" error for ipv6

I use buildx to build an alpine based multiplatform docker image for youtube-dl in the gitlab-ci.
If I run the image on a Raspberry 2 youtube-dl print the following error:

# youtube-dl -v --no-check-certificate https://www.youtube.com/watch?v=<vidoe_id>
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['-v', '--no-check-certificate', 'https://www.youtube.com/watch?v=rjv91XBT1xI']
[debug] Encodings: locale UTF-8, fs utf-8, out utf-8, pref UTF-8
[debug] youtube-dl version 2021.04.01
[debug] Python version 3.8.8 (CPython) - Linux-5.10.29-0-rpi2-armv7l-with
[debug] exe versions: ffmpeg 4.3.1, ffprobe 4.3.1
[debug] Proxy map: {}
[youtube] <vidoe_id>: Downloading webpage
WARNING: Unable to download webpage: <urlopen error [Errno 99] Address not available>
[youtube] <vidoe_id>: Downloading API JSON
ERROR: Unable to download API page: <urlopen error [Errno 99] Address not available> (caused by URLError(OSError(99, 'Address not available')))
  File "/usr/lib/python3.8/site-packages/youtube_dl/extractor/common.py", line 634, in _request_webpage
    return self._downloader.urlopen(url_or_request)
  File "/usr/lib/python3.8/site-packages/youtube_dl/YoutubeDL.py", line 2279, in urlopen
    return self._opener.open(req, timeout=self._socket_timeout)
  File "/usr/lib/python3.8/urllib/request.py", line 525, in open
    response = self._open(req, data)
  File "/usr/lib/python3.8/urllib/request.py", line 542, in _open
    result = self._call_chain(self.handle_open, protocol, protocol +
  File "/usr/lib/python3.8/urllib/request.py", line 502, in _call_chain
    result = func(*args)
  File "/usr/lib/python3.8/site-packages/youtube_dl/utils.py", line 2734, in https_open
    return self.do_open(functools.partial(
  File "/usr/lib/python3.8/urllib/request.py", line 1357, in do_open
    raise URLError(err)

After some test with wget inside the container, I notify this always happen if a program does use ipv6, but ipv4 seems to be fine:

# wget 'https://www.youtube.com'
Connecting to www.youtube.com ([2607:f8b0:4001:c0f::5b]:443)
wget: can't connect to remote host: Address not available

# wget 'https://loopsofzen.uk/' 
Connecting to loopsofzen.uk ([2001:8b0:0:30::666:102]:443)
wget: can't connect to remote host: Address not available

# wget 'https://docs.docker.com'
Connecting to docs.docker.com (13.224.193.38:443)
saving to 'index.html'
index.html           100% |**************************************************************************************************************| 32834  0:00:00 ETA
'index.html' saved

# wget 'https://www.google.com' && rm index.html 
Connecting to www.google.com (142.250.181.228:443)
saving to 'index.html'
index.html           100% |**************************************************************************************************************| 12935  0:00:00 ETA
'index.html' saved

If I build the image on my Raspberry without buildx, everything works fine.

Dockerfile:

FROM alpine
MAINTAINER kev <noreply@easypi.pro>

RUN set -xe \
    && apk add --no-cache ca-certificates \
                          ffmpeg \
                          openssl \
                          aria2 \
                          youtube-dl

# Try to run it so we know it works
RUN youtube-dl --version

WORKDIR /data

COPY entrypoint.sh /

RUN chmod +x /entrypoint.sh \
 && echo "* * * * * echo please mount cron tasks to /tasks.cron" >> /tasks.cron

RUN addgroup -g 1000 -S dockeruser \
 && adduser -h /data -u 1000 -S dockeruser -G dockeruser

ENTRYPOINT  ["/entrypoint.sh"]

.gitlab-ci.yml:

variables:
  DOCKER_DRIVER: overlay2
  DOCKER_HOST: tcp://docker:2375/

docker-build:
  # Use the docker image with buildx for multiplatform build.
  image: lukas1818/docker-with-buildx:latest
  stage: build
  services:
    - docker:dind
  before_script:
    - docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY
  # Default branch leaves tag empty (= latest tag)
  # All other branches are tagged with the escaped branch name (commit ref slug)
  script:
    - |
      if [[ "$CI_COMMIT_BRANCH" == "$CI_DEFAULT_BRANCH" ]]; then
        tag=""
        echo "Running on default branch '$CI_DEFAULT_BRANCH': tag = 'latest'"
      else
        tag=":$CI_COMMIT_REF_SLUG"
        echo "Running on branch '$CI_COMMIT_BRANCH': tag = $tag"
      fi
    - docker run --rm --privileged multiarch/qemu-user-static --reset -p yes; docker buildx create --use
    - docker buildx build --push --platform linux/arm/v7,linux/arm64/v8,linux/amd64 --tag "$CI_REGISTRY_IMAGE${tag}" .
  # Run this job in a branch where a Dockerfile exists
  retry: 2
  rules:
    - if: $CI_COMMIT_BRANCH
      exists:
        - Dockerfile

A debian based stubby image have also connection issues on my Raspberry if it was build with buildx.

Start by reproducing the IPv6 failure with the Dockerfile and .gitlab-ci.yml buildx command on the Raspberry Pi targets, comparing IPv4 and IPv6 connections inside the resulting images. Trace the buildx and QEMU-based multiplatform path before changing anything. Done means images built with buildx can establish IPv6 connections as well as images built natively.