diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2849d6e24b..42683e537b 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -41,24 +41,24 @@ jobs:
         run: echo "$TITLE" | commitlint --verbose
 
   format:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@master
         with:
           components: rustfmt
           toolchain: nightly-2024-01-12
-      - uses: Swatinem/rust-cache@v2
+      # - uses: Swatinem/rust-cache@v2
       - run: scripts/rust_fmt.sh --check
 
   clippy:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@stable
         with:
           components: clippy
-      - uses: Swatinem/rust-cache@v2
+      # - uses: Swatinem/rust-cache@v2
 
       # Setup pypy and link to the location expected by .cargo/config.toml.
       - uses: actions/setup-python@v5
@@ -73,7 +73,7 @@ jobs:
       - run: scripts/clippy.sh
 
   run-python-tests:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
@@ -85,11 +85,11 @@ jobs:
       - run: pytest scripts/merge_paths_test.py
 
   run-tests:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@stable
-      - uses: Swatinem/rust-cache@v2
+      # - uses: Swatinem/rust-cache@v2
 
       # Setup pypy and link to the location expected by .cargo/config.toml.
       - uses: actions/setup-python@v5
@@ -110,7 +110,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@stable
 
-      - uses: Swatinem/rust-cache@v2
+      # - uses: Swatinem/rust-cache@v2
 
       - name: Build native blockifier
         run: ./build_native_blockifier.sh
diff --git a/.github/workflows/compiled_cairo.yml b/.github/workflows/compiled_cairo.yml
index 747c6349cf..0017648e8e 100644
--- a/.github/workflows/compiled_cairo.yml
+++ b/.github/workflows/compiled_cairo.yml
@@ -17,18 +17,25 @@ on:
 
 jobs:
   verify_cairo_file_dependencies:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@master
         with:
           components: rustfmt
           toolchain: nightly-2024-01-12
-      - uses: Swatinem/rust-cache@v2
-      - uses: actions/setup-python@v4
+      # - uses: Swatinem/rust-cache@v2
+
+      # Setup pypy and link to the location expected by .cargo/config.toml.
+      - uses: actions/setup-python@v5
+        id: setup-pypy
         with:
-          python-version: '3.9'
-          cache: 'pip'
+          python-version: 'pypy3.9'
+      - run: ln -s '${{ steps.setup-pypy.outputs.python-path }}' /usr/local/bin/pypy3.9
+      - env:
+          LD_LIBRARY_PATH: ${{ env.Python3_ROOT_DIR }}/bin
+        run: echo "LD_LIBRARY_PATH=${LD_LIBRARY_PATH}" >> $GITHUB_ENV
+
       - run:
           pip install -r crates/blockifier/tests/requirements.txt;
           cargo test verify_feature_contracts -- --include-ignored
diff --git a/.github/workflows/coverage.yml b/.github/workflows/coverage.yml
index 1e2bbc89e8..3461347227 100644
--- a/.github/workflows/coverage.yml
+++ b/.github/workflows/coverage.yml
@@ -4,22 +4,33 @@ on: [pull_request, push]
 
 jobs:
   coverage:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     env:
       CARGO_TERM_COLOR: always
     steps:
       - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@stable
-      - uses: Swatinem/rust-cache@v2
+      # - uses: Swatinem/rust-cache@v2
+
+      # Setup pypy and link to the location expected by .cargo/config.toml.
+      - uses: actions/setup-python@v5
+        id: setup-pypy
+        with:
+          python-version: 'pypy3.9'
+      - run: ln -s '${{ steps.setup-pypy.outputs.python-path }}' /usr/local/bin/pypy3.9
+      - env:
+          LD_LIBRARY_PATH: ${{ steps.setup-pypy.outputs.pythonLocation }}/bin
+        run: echo "LD_LIBRARY_PATH=${LD_LIBRARY_PATH}" >> $GITHUB_ENV
+
       - name: Install cargo-llvm-cov
         uses: taiki-e/install-action@cargo-llvm-cov
-      - name: Generate code coverage
-        run: cargo llvm-cov --codecov --output-path codecov.json
-        env:
-          SEED: 0
-      - name: Upload coverage to Codecov
-        uses: codecov/codecov-action@v3
-        with:
-          token: ${{ secrets.CODECOV_TOKEN }}
-          verbose: true
-          fail_ci_if_error: true
+      # - name: Generate code coverage
+      #   run: cargo llvm-cov --codecov --output-path codecov.json
+      #   env:
+      #     SEED: 0
+      # - name: Upload coverage to Codecov
+      #   uses: codecov/codecov-action@v3
+      #   with:
+      #     token: ${{ secrets.CODECOV_TOKEN }}
+      #     verbose: true
+      #     fail_ci_if_error: true
diff --git a/.github/workflows/post-merge.yml b/.github/workflows/post-merge.yml
index b93bc4680d..915e3e4651 100644
--- a/.github/workflows/post-merge.yml
+++ b/.github/workflows/post-merge.yml
@@ -7,18 +7,25 @@ on:
 jobs:
   if_merged:
     if: github.event.pull_request.merged == true
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@master
         with:
           components: rustfmt
           toolchain: nightly-2024-01-12
-      - uses: Swatinem/rust-cache@v2
-      - uses: actions/setup-python@v4
+      # - uses: Swatinem/rust-cache@v2
+
+      # Setup pypy and link to the location expected by .cargo/config.toml.
+      - uses: actions/setup-python@v5
+        id: setup-pypy
         with:
-          python-version: '3.9'
-          cache: 'pip'
+          python-version: 'pypy3.9'
+      - run: ln -s '${{ steps.setup-pypy.outputs.python-path }}' /usr/local/bin/pypy3.9
+      - env:
+          LD_LIBRARY_PATH: ${{ env.Python3_ROOT_DIR }}/bin
+        run: echo "LD_LIBRARY_PATH=${LD_LIBRARY_PATH}" >> $GITHUB_ENV
+
       - run:
           pip install -r crates/blockifier/tests/requirements.txt;
           cargo test -- --include-ignored