diff --git a/.github/workflows/pypi-upload.yml b/.github/workflows/pypi-upload.yml
index 28b84753..df39f25c 100644
--- a/.github/workflows/pypi-upload.yml
+++ b/.github/workflows/pypi-upload.yml
@@ -17,13 +17,13 @@ jobs:
     runs-on: ubuntu-latest
     name: deploy
     steps:
-    - uses: actions/checkout@master
+    - uses: actions/checkout@v3
       with:
         # To generate a valid version number setuptools_scm needs sufficient
         # git history.
         fetch-depth: 0
     - name: Set up Python
-      uses: actions/setup-python@v2
+      uses: actions/setup-python@v4
       with:
         python-version: "3.9"
     - name: Install pypa/build
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 98243e0d..0a6fe609 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -5,16 +5,24 @@ name: Tests
 
 on:
   push:
-    branches:
-      - master
-      - 'stable/**'
+    # branches:
+    #   - master
+    #   - 'stable/**'
   pull_request:
     branches:
       - master
       - 'stable/**'
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.ref }}
+  cancel-in-progress: true
+
 jobs:
   tests:
+    # Run on external PRs, but not on internal PRs (since that would duplicate push-triggered runs)
+    if:
+      github.event_name == 'push' || github.event.pull_request.head.repo.full_name != github.repository
+
     name: ${{matrix.extra_name}}${{matrix.sim}} (${{matrix.sim-version}}) | ${{matrix.os}} | Python ${{matrix.python-version}} ${{matrix.may_fail && '| May Fail' || ''}}
     runs-on: ${{matrix.os}}
     env:
@@ -23,12 +31,14 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.6", "3.12"]
+        # python-version: ["3.6", "3.12"]
         include:
         - sim: icarus
           sim-version: apt
+          python-version: ["3.6", "3.12"]
+          # python-version: "3.6"
           lang: verilog
-          os: ubuntu-22.04
+          os: ubuntu-20.04
     steps:
     - uses: actions/checkout@v3
     - uses: actions/setup-python@v4
@@ -45,7 +55,7 @@ jobs:
       env:
         DEBIAN_FRONTEND: noninteractive
       run: |
-        sudo apt-get install --yes iverilog
+        sudo apt-get install --yes --no-install-recommends iverilog
     - name: Install testing requirements
       run: |
         pip install nox