Cannot add py7zr library to flatpak

[Allexio]

Hi there,
I'm currently trying to add support for 7zip extraction but I have some trouble getting the py7zr library included in my flatpak.

Everything works great with my initial 3 libraries: pyyaml requests rarfile but as soon as I add py7zr to the flatpak things go awry.
Of course it works in my dev python environment (like, I was able to install the pip packages and their dependencies just fine).

Initial com.nomm.Nomm.yaml

id: com.nomm.Nomm
runtime: org.gnome.Platform
runtime-version: '49' # Matching the latest stable GNOME runtime
sdk: org.gnome.Sdk
command: nomm # The name of your entry-point script
finish-args:
  # Network access for downloading images and Nexus mods
  - --share=network
  - --share=ipc
  - --socket=fallback-x11
  - --socket=wayland
  - --device=dri
  # Access to Steam and Heroic configurations
  - --filesystem=home:ro
  # Specific permission for Heroic's Flatpak config if Heroic is also a Flatpak
  - --filesystem=~/.var/app/com.heroicgameslauncher.hgl/config/heroic:ro
  - --filesystem=xdg-run/app/com.heroicgameslauncher.hgl:ro
  - --own-name=com.nomm.Nomm
  # Access to Steam
  - --filesystem=~/.local/share/Steam:ro
  # Flatpak Steam path (if the user is running Steam as a Flatpak)
  - --filesystem=~/.var/app/com.valvesoftware.Steam:ro
  - --filesystem=xdg-run/app/com.valvesoftware.Steam:ro
  # mounting points
  - --filesystem=/run/media:rw
  - --filesystem=/mnt:rw

modules:

  # Python dependencies (generated via flatpak-pip-generator)
  - python3-modules.json

  # bundling unrar because otherwise the default version in flatpak doesn't work
  - name: unrar
    buildsystem: simple
    build-commands:
      - make -f makefile
      - install -Dm755 unrar /app/bin/unrar
    sources:
      - type: archive
        url: https://www.rarlab.com/rar/unrarsrc-6.2.10.tar.gz
        sha256: 55fe6ebd5e48d6655bfda3fd19b55438ca05e13c7e69772420caad9fdb68ef42
        
  # Application
  - name: nomm
    buildsystem: simple

    build-commands:
      # Install entry point from the src folder to /app/bin
      - install -D src/launcher.py /app/bin/nomm
      
      # Install desktop file
      - install -D com.nomm.Nomm.desktop /app/share/applications/com.nomm.Nomm.desktop

      # Install metainfo
      - install -D com.nomm.Nomm.metainfo.xml /app/share/metainfo/com.nomm.Nomm.metainfo.xml

      # Install icon
      - install -D assets/nomm.png /app/share/icons/hicolor/64x64/apps/com.nomm.Nomm.png
      
      # Copy all the important stuff
      - cp src/*.py /app/bin/
      - cp src/*.yaml /app/bin/
      - cp src/*.css /app/bin/
      
      - cp -r assets /app/bin/assets
      - cp -r default_game_configs /app/bin/default_game_configs
    sources:
      - type: dir
        path: .

command to generate python3-modules.json:
./flatpak-pip-generator.py pyyaml requests rarfile py7zr
command to build flatpak:
flatpak-builder --user --install --force-clean --repo=repo build-dir com.nomm.Nomm.yaml

With this I got the following error:

ERROR: Could not find a version that satisfies the requirement backports.zstd>=1.0.0; python_version < "3.14" (from py7zr) (from versions: none)
ERROR: No matching distribution found for backports.zstd>=1.0.0; python_version < "3.14"

So I decided to manually add backports.zstd to my modules in my com.nomm.Nomm.yaml:

- name: python3-backports-zstd
    buildsystem: simple
    build-commands:
      - pip3 install --prefix=/app --no-build-isolation --no-deps .
    sources:
      - type: archive
        url: https://files.pythonhosted.org/packages/f4/b1/36a5182ce1d8ef9ef32bff69037bd28b389bbdb66338f8069e61da7028cb/backports_zstd-1.3.0.tar.gz
        sha256: e8b2d68e2812f5c9970cabc5e21da8b409b5ed04e79b4585dbffa33e9b45ebe2

(I added --no-build-isolation to avoid issues with it trying to connect to pip and failing which was generating another error)
Unfortunately this has just moved the problem to a second dependency:

creating '/tmp/pip-modern-metadata-z4kc3x4w/pyppmd-0.0.0.dist-info'
  Preparing metadata (pyproject.toml) ... done
  WARNING: Requested pyppmd>=1.3.1 from file:///run/build/python3-py7zr/pyppmd-1.3.1.tar.gz (from py7zr), but installing version 0.0.0
Discarding file:///run/build/python3-py7zr/pyppmd-1.3.1.tar.gz: Requested pyppmd>=1.3.1 from file:///run/build/python3-py7zr/pyppmd-1.3.1.tar.gz (from py7zr) has inconsistent version: expected '1.3.1', but metadata has '0.0.0'
INFO: pip is looking at multiple versions of py7zr to determine which version is compatible with other requirements. This could take a while.
ERROR: Could not find a version that satisfies the requirement pyppmd>=1.3.1 (from py7zr) (from versions: 1.3.1)
ERROR: No matching distribution found for pyppmd>=1.3.1
Error: module python3-py7zr: Child process exited with code 1

I therefore tried to also manually include pyppmd in my modules as such:

- name: python3-pyppmd
    buildsystem: simple
    build-commands:
      # Use no-build-isolation to avoid needing internet for build-time deps
      - pip3 install --prefix=/app --no-build-isolation --no-deps .
    sources:
      - type: archive
        url: https://files.pythonhosted.org/packages/81/d7/803232913cab9163a1a97ecf2236cd7135903c46ac8d49613448d88e8759/pyppmd-1.3.1.tar.gz
        sha256: ced527f08ade4408c1bfc5264e9f97ffac8d221c9d13eca4f35ec1ec0c7b6b2e
        subdir: pyppmd-1.3.1

... but I still get the same error.
I've tried other ideas to try and get past this but nothing worked out 😔

Any help from a flatpak expert would be very much appreciated.

[Allexio]

(yes, I know the permissions are all over the place, I need to go over them and actually analyse what I really need, but tbh right now I just want things to work x)