diff --git a/.github/workflows/build-ruby.yml b/.github/workflows/build-ruby.yml
index 65a4422..416f81b 100644
--- a/.github/workflows/build-ruby.yml
+++ b/.github/workflows/build-ruby.yml
@@ -159,11 +159,6 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
 
-      # Using docker-container engine enables advanced buildx features
-      - name: Set up Docker container engine
-        run: |
-          docker buildx create --name=container --driver=docker-container --use --bootstrap
-
       # First, build image for x86_64 as it will fail fast
       #
       # Tagging is necessary to reference the image for the testing step
@@ -171,11 +166,11 @@ jobs:
       - name: Build single-arch image (x86_64)
         if: ${{ contains(matrix.arch, 'x86_64') }}
         run: |
-          docker buildx build ${{ steps.vars.outputs.SRC }} --builder=container --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }} --output=type=image,push=false --platform linux/x86_64 -f ${{ steps.vars.outputs.DOCKERFILE }}
+          docker buildx build ${{ steps.vars.outputs.SRC }} --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }} --output=type=image,push=false --platform linux/x86_64 -f ${{ steps.vars.outputs.DOCKERFILE }}
       - name: Tag single-arch image (x86_64)
         if: ${{ contains(matrix.arch, 'x86_64') }}
         run: |
-          docker buildx build ${{ steps.vars.outputs.SRC }} --builder=container --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }} --load --platform linux/x86_64 -f ${{ steps.vars.outputs.DOCKERFILE }} --tag ${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.TAG }}
+          docker buildx build ${{ steps.vars.outputs.SRC }} --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }} --load --platform linux/x86_64 -f ${{ steps.vars.outputs.DOCKERFILE }} --tag ${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.TAG }}
       - name: Test single-arch image (x86_64)
         if: ${{ contains(matrix.arch, 'x86_64') }}
         run: |
@@ -190,13 +185,13 @@ jobs:
       - name: Tag single-arch image (x86_64)
         if: ${{ contains(matrix.arch, 'x86_64') }}
         run: |
-          docker buildx build ${{ steps.vars.outputs.SRC }} --builder=container --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }} --load --platform linux/x86_64 -f ${{ steps.vars.outputs.DOCKERFILE }} --tag ${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }}
+          docker buildx build ${{ steps.vars.outputs.SRC }} --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }} --load --platform linux/x86_64 -f ${{ steps.vars.outputs.DOCKERFILE }} --tag ${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }}
           docker image list
       - name: Build single-arch compiler image (x86_64)
         if: ${{ contains(matrix.arch, 'x86_64') && matrix.libc == 'musl' }}
         run: |
-          docker image list
-          docker buildx build ${{ steps.vars.outputs.SRC }} --builder=container --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }}-gcc --output=type=image,push=false --platform linux/x86_64 -f ${{ steps.vars.outputs.DOCKERFILE }}.gcc
+          docker image list # image not in builder=container!
+          docker buildx build ${{ steps.vars.outputs.SRC }} --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }}-gcc --output=type=image,push=false --platform linux/x86_64 -f ${{ steps.vars.outputs.DOCKERFILE }}.gcc
       # TODO: add CI tag and test
 
       # Then, build image for aarch64 which, being emulated under qemu, is slower
@@ -211,11 +206,11 @@ jobs:
       - name: Build single-arch image (aarch64)
         if: ${{ contains(matrix.arch, 'aarch64') }}
         run: |
-          docker buildx build ${{ steps.vars.outputs.SRC }} --builder=container --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }} --output=type=image,push=false --platform linux/aarch64 -f ${{ steps.vars.outputs.DOCKERFILE }}
+          docker buildx build ${{ steps.vars.outputs.SRC }} --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }} --output=type=image,push=false --platform linux/aarch64 -f ${{ steps.vars.outputs.DOCKERFILE }}
       - name: Tag single-arch image (aarch64)
         if: ${{ contains(matrix.arch, 'aarch64') }}
         run: |
-          docker buildx build ${{ steps.vars.outputs.SRC }}  --builder=container --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }} --load --platform linux/aarch64 -f ${{ steps.vars.outputs.DOCKERFILE }} --tag ${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.TAG }}
+          docker buildx build ${{ steps.vars.outputs.SRC }} --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }} --load --platform linux/aarch64 -f ${{ steps.vars.outputs.DOCKERFILE }} --tag ${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.TAG }}
       - name: Test single-arch image (aarch64)
         if: ${{ contains(matrix.arch, 'aarch64') }}
         run: |
@@ -230,11 +225,11 @@ jobs:
       - name: Tag single-arch image (aarch64)
         if: ${{ contains(matrix.arch, 'aarch64') }}
         run: |
-          docker buildx build ${{ steps.vars.outputs.SRC }}  --builder=container --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }} --load --platform linux/aarch64 -f ${{ steps.vars.outputs.DOCKERFILE }} --tag ${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }}
+          docker buildx build ${{ steps.vars.outputs.SRC }} --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }} --load --platform linux/aarch64 -f ${{ steps.vars.outputs.DOCKERFILE }} --tag ${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }}
       - name: Build single-arch compiler image (aarch64)
         if: ${{ contains(matrix.arch, 'aarch64') && matrix.libc == 'musl' }}
         run: |
-          docker buildx build ${{ steps.vars.outputs.SRC }} --builder=container --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }}-gcc --output=type=image,push=false --platform linux/aarch64 -f ${{ steps.vars.outputs.DOCKERFILE }}.gcc
+          docker buildx build ${{ steps.vars.outputs.SRC }} --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }}-gcc --output=type=image,push=false --platform linux/aarch64 -f ${{ steps.vars.outputs.DOCKERFILE }}.gcc
       # TODO: add CI tag and test
 
       # Finally, assemble multi-arch image for a combined push to the registry
@@ -245,26 +240,26 @@ jobs:
           echo ${{ secrets.GITHUB_TOKEN }} | docker login ${{ env.REGISTRY }} -u ${{ github.actor }} --password-stdin
       - name: Push CI run image (${{ join(matrix.arch, ', ') }})
         run: |
-          docker buildx build ${{ steps.vars.outputs.SRC }} --builder=container --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }} --output=type=image,push=true --build-arg BUILDKIT_INLINE_CACHE=1 --platform ${{ steps.vars.outputs.DOCKER_PLATFORMS }} -f ${{ steps.vars.outputs.DOCKERFILE }} --tag ${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.TAG }}
+          docker buildx build ${{ steps.vars.outputs.SRC }} --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }} --output=type=image,push=true --build-arg BUILDKIT_INLINE_CACHE=1 --platform ${{ steps.vars.outputs.DOCKER_PLATFORMS }} -f ${{ steps.vars.outputs.DOCKERFILE }} --tag ${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.TAG }}
       - name: Push release image (${{ join(matrix.arch, ', ') }})
         if: ${{ inputs.push }}
         run: |
-          docker buildx build ${{ steps.vars.outputs.SRC }} --builder=container --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }} --output=type=image,push=true --build-arg BUILDKIT_INLINE_CACHE=1 --platform ${{ steps.vars.outputs.DOCKER_PLATFORMS }} -f ${{ steps.vars.outputs.DOCKERFILE }} --tag ${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }}
+          docker buildx build ${{ steps.vars.outputs.SRC }} --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }} --output=type=image,push=true --build-arg BUILDKIT_INLINE_CACHE=1 --platform ${{ steps.vars.outputs.DOCKER_PLATFORMS }} -f ${{ steps.vars.outputs.DOCKERFILE }} --tag ${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }}
 
       # TODO: hardcoded, reuse strip-tags directive instead (or better, unify gnu)
       - name: Push unqualified release image (${{ join(matrix.arch, ', ') }})
         if: ${{ inputs.push && matrix.libc == 'gnu' }}
         run: |
-          docker buildx build ${{ steps.vars.outputs.SRC }} --builder=container --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }} --output=type=image,push=true --build-arg BUILDKIT_INLINE_CACHE=1 --platform ${{ steps.vars.outputs.DOCKER_PLATFORMS }} -f ${{ steps.vars.outputs.DOCKERFILE }} --tag ${{ steps.vars.outputs.IMAGE }}:${{ matrix.version }}
+          docker buildx build ${{ steps.vars.outputs.SRC }} --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }} --output=type=image,push=true --build-arg BUILDKIT_INLINE_CACHE=1 --platform ${{ steps.vars.outputs.DOCKER_PLATFORMS }} -f ${{ steps.vars.outputs.DOCKERFILE }} --tag ${{ steps.vars.outputs.IMAGE }}:${{ matrix.version }}
 
       # TODO: hardcoded, reuse append-tags directive instead (or better, unify gnu)
       - name: Push release compiler image (${{ join(matrix.arch, ', ') }})
         if: ${{ inputs.push && matrix.libc == 'gnu' }}
         run: |
-          docker buildx build ${{ steps.vars.outputs.SRC }} --builder=container --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }}-gcc --output=type=image,push=true --build-arg BUILDKIT_INLINE_CACHE=1 --platform ${{ steps.vars.outputs.DOCKER_PLATFORMS }} -f ${{ steps.vars.outputs.DOCKERFILE }} --tag ${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }}-gcc
+          docker buildx build ${{ steps.vars.outputs.SRC }} --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }}-gcc --output=type=image,push=true --build-arg BUILDKIT_INLINE_CACHE=1 --platform ${{ steps.vars.outputs.DOCKER_PLATFORMS }} -f ${{ steps.vars.outputs.DOCKERFILE }} --tag ${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }}-gcc
 
       # TODO: hardcoded musl, unify gnu instead
       - name: Push release compiler image (${{ join(matrix.arch, ', ') }})
         if: ${{ inputs.push && matrix.libc == 'musl' }}
         run: |
-          docker buildx build ${{ steps.vars.outputs.SRC }} --builder=container --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }}-gcc --output=type=image,push=true --build-arg BUILDKIT_INLINE_CACHE=1 --platform ${{ steps.vars.outputs.DOCKER_PLATFORMS }} -f ${{ steps.vars.outputs.DOCKERFILE }}.gcc --tag ${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }}-gcc
+          docker buildx build ${{ steps.vars.outputs.SRC }} --cache-from=type=registry,ref=${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }}-gcc --output=type=image,push=true --build-arg BUILDKIT_INLINE_CACHE=1 --platform ${{ steps.vars.outputs.DOCKER_PLATFORMS }} -f ${{ steps.vars.outputs.DOCKERFILE }}.gcc --tag ${{ steps.vars.outputs.IMAGE }}:${{ steps.vars.outputs.RELEASE_TAG }}-gcc