diff --git a/.github/workflows/conda-ubuntu-macos.yml b/.github/workflows/conda-ubuntu-macos.yml
index 41a25cf47..64a2b3a3e 100644
--- a/.github/workflows/conda-ubuntu-macos.yml
+++ b/.github/workflows/conda-ubuntu-macos.yml
@@ -22,10 +22,14 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: ["ubuntu-latest", "macos-latest"]
+        # os: ["ubuntu-latest", "macos-latest"] 2024-04-26 macos-latest failing
+        # Error: No installed conda 'base' environment found ...; see
+        # https://github.com/coin-or/CppAD/actions/runs/8834404014/job/24281915299
+
+        os: ["ubuntu-latest"]
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
 
     - name: Checkout submodules
       run: |
diff --git a/.github/workflows/conda-windows-clang.yml b/.github/workflows/conda-windows-clang.yml
index 0c7ae3fda..9ba7bb3b2 100644
--- a/.github/workflows/conda-windows-clang.yml
+++ b/.github/workflows/conda-windows-clang.yml
@@ -24,7 +24,7 @@ jobs:
             compiler: clang-cl
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - name: Checkout submodules
       run: |
         git submodule update --init
diff --git a/.github/workflows/conda-windows-eigen.yml b/.github/workflows/conda-windows-eigen.yml
index f816b0b71..c24a3cf2d 100644
--- a/.github/workflows/conda-windows-eigen.yml
+++ b/.github/workflows/conda-windows-eigen.yml
@@ -10,7 +10,7 @@ jobs:
     runs-on: windows-2019
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - uses: conda-incubator/setup-miniconda@v2
       with:
         activate-environment: conda_env
diff --git a/.github/workflows/conda-windows-v142.yml b/.github/workflows/conda-windows-v142.yml
index cf2bcd998..757fa37d1 100644
--- a/.github/workflows/conda-windows-v142.yml
+++ b/.github/workflows/conda-windows-v142.yml
@@ -23,7 +23,7 @@ jobs:
             os: windows-2019
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - name: Checkout submodules
       run: |
         git submodule update --init
diff --git a/.github/workflows/ubuntu-macos.yml b/.github/workflows/ubuntu-macos.yml
index e52503b52..fba96fc2e 100644
--- a/.github/workflows/ubuntu-macos.yml
+++ b/.github/workflows/ubuntu-macos.yml
@@ -13,7 +13,7 @@ jobs:
         os: [ ubuntu-latest, macos-latest ]
     steps:
       - name: Check out repository code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
       - name: set debug_which
         run: |
           mkdir build
diff --git a/.github/workflows/uraimo_linux.yml b/.github/workflows/uraimo_linux.yml
index d4e33983e..9b7df1cd0 100644
--- a/.github/workflows/uraimo_linux.yml
+++ b/.github/workflows/uraimo_linux.yml
@@ -21,7 +21,7 @@ jobs:
             distro: alpine_latest
     steps:
       - name: Check out repository code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
       - name: Checkout uraimo
         uses: uraimo/run-on-arch-action@v2
       - name: set debug_which
diff --git a/.github/workflows/windows-msys2.yml b/.github/workflows/windows-msys2.yml
index 75e152dbb..8667fba9e 100644
--- a/.github/workflows/windows-msys2.yml
+++ b/.github/workflows/windows-msys2.yml
@@ -14,7 +14,7 @@ jobs:
       run:
         shell: msys2 {0}
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: msys2/setup-msys2@v2
         with:
           msystem: MINGW64