Try another approach

.github/workflows/container.yml

@@ -17,25 +17,11 @@ jobs:
       matrix:
         platform: [linux/amd64, linux/386, linux/arm64, linux/arm/v6, linux/arm/v7]
     steps:
-      - name: Checkout Repository
-        uses: actions/checkout@v2
-
       - name: Declare platform
         run: |
           platform=${{ matrix.platform }}
           echo "PLATFORM=${platform//\//-}" >> $GITHUB_ENV
 
-      - name: Create pip cache directory
-        run: mkdir -p /tmp/pip-cache
-
-      - name: Cache pip artifacts
-        uses: actions/cache@v4
-        with:
-          path: /tmp/pip-cache
-          key: pip-cache-${{ env.PLATFORM }}-${{ hashFiles('**/requirements.txt') }}
-          restore-keys: |
-            pip-cache-${{ env.PLATFORM }}-
-
       - name: Setup QEMU
         uses: docker/setup-qemu-action@v3
 
@@ -60,9 +46,10 @@ jobs:
         uses: docker/build-push-action@v6
         with:
           platforms: ${{ matrix.platform }}
-          build-contexts: pip-cache=/tmp/pip-cache
           labels: ${{ steps.meta.outputs.labels }}
           outputs: type=image,name=ghcr.io/${{ github.repository }},push-by-digest=true,name-canonical=true,push=${{ github.event_name != 'pull_request' && 'true' || 'false' }}
+          cache-from: type=registry,ref=ghcr.io/${{ github.repository }}:buildcache-${{ env.PLATFORM }}
+          cache-to: type=registry,ref=ghcr.io/${{ github.repository }}:buildcache-${{ env.PLATFORM }},mode=max
 
       - name: Export digest
         if: ${{ github.event_name != 'pull_request' }}

Dockerfile

@@ -29,7 +29,7 @@ COPY auto_rx/requirements.txt \
   /root/radiosonde_auto_rx/auto_rx/requirements.txt
 
 # Install Python packages.
-RUN --mount=type=cache,target=/root/.cache/pip,from=pip-cache pip3 install \
+RUN pip3 install \
   --user --break-system-packages --no-warn-script-location --ignore-installed \
   -r /root/radiosonde_auto_rx/auto_rx/requirements.txt