diff --git a/.github/workflows/build_and_test.yaml b/.github/workflows/build_and_test.yaml
index 208ba0b355..608b6baa44 100644
--- a/.github/workflows/build_and_test.yaml
+++ b/.github/workflows/build_and_test.yaml
@@ -15,6 +15,13 @@ on:
         description: "The ref to build and test."
         required: False
 
+# If another instance of this workflow is started for the same PR, cancel the
+# old one.  If a PR is updated and a new test run is started, the old test run
+# will be cancelled automatically to conserve resources.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.inputs.ref || github.ref }}
+  cancel-in-progress: true
+
 jobs:
   lint:
     name: Lint
@@ -40,9 +47,10 @@ jobs:
       fail-fast: false
       matrix:
         # NOTE: macos-10.15 is required for now, to work around issues with our
-        # build system.  See related comments in
+        # build system.  The same is true for windows-2019.  See related
+        # comments in
         # .github/workflows/custom-actions/build-packager/action.yaml
-        os: ["ubuntu-latest", "macos-10.15", "windows-latest", "self-hosted-linux-arm64"]
+        os: ["ubuntu-latest", "macos-10.15", "windows-2019", "self-hosted-linux-arm64"]
         build_type: ["Debug", "Release"]
         lib_type: ["static", "shared"]
         include:
@@ -56,7 +64,7 @@ jobs:
             target_arch: x64
             exe_ext: ""
             build_type_suffix: ""
-          - os: windows-latest
+          - os: windows-2019
             os_name: win
             target_arch: x64
             exe_ext: ".exe"
diff --git a/.github/workflows/custom-actions/build-docs/action.yaml b/.github/workflows/custom-actions/build-docs/action.yaml
index 3b68b588eb..d2edf0199b 100644
--- a/.github/workflows/custom-actions/build-docs/action.yaml
+++ b/.github/workflows/custom-actions/build-docs/action.yaml
@@ -17,7 +17,6 @@ runs:
         python3 -m pip install \
             sphinxcontrib.plantuml \
             recommonmark \
-            cloud_sptheme \
             breathe
         echo "::endgroup::"
 
diff --git a/.github/workflows/custom-actions/build-packager/action.yaml b/.github/workflows/custom-actions/build-packager/action.yaml
index 0556ae86b1..a0fe8da802 100644
--- a/.github/workflows/custom-actions/build-packager/action.yaml
+++ b/.github/workflows/custom-actions/build-packager/action.yaml
@@ -76,6 +76,8 @@ runs:
         echo "${GITHUB_WORKSPACE}/depot_tools" >> $GITHUB_PATH
         # Bypass VPYTHON included by depot_tools.  Prefer the system installation.
         echo "VPYTHON_BYPASS=manually managed python not supported by chrome operations" >> $GITHUB_ENV
+        # Work around an issue in depot_tools on Windows, where an unexpected exception type appears.
+        sed -e 's/except subprocess.CalledProcessError:/except:/' -i.bk depot_tools/git_cache.py
         echo "::endgroup::"
 
     - name: Build ninja (arm only)
diff --git a/.github/workflows/github_release.yaml b/.github/workflows/github_release.yaml
index 0d018670c6..937d62d566 100644
--- a/.github/workflows/github_release.yaml
+++ b/.github/workflows/github_release.yaml
@@ -112,7 +112,7 @@ jobs:
     needs: [setup, lint, draft_release]
     strategy:
       matrix:
-        os: ["ubuntu-latest", "macos-latest", "windows-latest", "self-hosted-linux-arm64"]
+        os: ["ubuntu-latest", "macos-latest", "windows-2019", "self-hosted-linux-arm64"]
         build_type: ["Debug", "Release"]
         lib_type: ["static", "shared"]
         include:
@@ -126,7 +126,7 @@ jobs:
             target_arch: x64
             exe_ext: ""
             build_type_suffix: ""
-          - os: windows-latest
+          - os: windows-2019
             os_name: win
             target_arch: x64
             exe_ext: ".exe"
diff --git a/docs/source/conf.py b/docs/source/conf.py
index 5a35ff599f..92aff35f9e 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -35,7 +35,6 @@ extensions = ['sphinx.ext.autodoc',
               'sphinx.ext.githubpages',
               'sphinxcontrib.plantuml',
               'recommonmark',
-              'cloud_sptheme.ext.table_styling',
               'breathe']
 
 # Breathe configurations.
diff --git a/packager/testing/dockers/ArchLinux_Dockerfile b/packager/testing/dockers/ArchLinux_Dockerfile
deleted file mode 100644
index 1b0435687e..0000000000
--- a/packager/testing/dockers/ArchLinux_Dockerfile
+++ /dev/null
@@ -1,22 +0,0 @@
-FROM archlinux:latest
-
-# Install utilities, libraries, and dev tools.
-RUN pacman -Sy --needed --noconfirm \
-        core/which \
-        c-ares \
-        gcc git python2 python3
-
-# Default to python2 because our build system is ancient.
-RUN ln -sf python2 /usr/bin/python
-
-# Install depot_tools.
-WORKDIR /
-RUN git clone -b chrome/4147 https://chromium.googlesource.com/chromium/tools/depot_tools.git
-RUN touch depot_tools/.disable_auto_update
-ENV PATH /depot_tools:$PATH
-
-# Bypass VPYTHON included by depot_tools.  Prefer the system installation.
-ENV VPYTHON_BYPASS="manually managed python not supported by chrome operations"
-
-# Build and run this docker by mapping shaka-packager with
-# -v "shaka-packager:/shaka-packager".
diff --git a/packager/testing/dockers/test_dockers.sh b/packager/testing/dockers/test_dockers.sh
index 3cf38bc4ad..29fd7e12e7 100755
--- a/packager/testing/dockers/test_dockers.sh
+++ b/packager/testing/dockers/test_dockers.sh
@@ -7,7 +7,11 @@ SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 PACKAGER_DIR="$(dirname "$(dirname "$(dirname "$(dirname ${SCRIPT_DIR})")")")"
 
 function docker_run() {
-  docker run -v ${PACKAGER_DIR}:/shaka-packager -w /shaka-packager/src ${CONTAINER} "$@"
+  docker run \
+    -v ${PACKAGER_DIR}:/shaka-packager \
+    -w /shaka-packager/src \
+    --user $(id -u):$(id -g) \
+    ${CONTAINER} "$@"
 }
 
 # Command line arguments will be taken as an allowlist of OSes to run.