The registry is not in the environment context, but in the variable context here

.github/workflows/ci.yml

@@ -23,13 +23,13 @@ jobs:
         id: meta
         uses: docker/metadata-action@v5
         with:
-          images: ${{ env.REGISTRY }}/${{ github.repository }}
+          images: ${{ vars.REGISTRY }}/${{ github.repository }}
       -
         name: Login to DockerHub
         if: github.event_name != 'pull_request'
         uses: docker/login-action@v3
         with:
-          registry: ${{ env.REGISTRY }}
+          registry: ${{ vars.REGISTRY }}
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
       -