diff --git a/.github/workflows/release-artifacts.yml b/.github/workflows/release-artifacts.yml
index f292d703ed..325c1f7d39 100644
--- a/.github/workflows/release-artifacts.yml
+++ b/.github/workflows/release-artifacts.yml
@@ -3,28 +3,33 @@
 name: Build release artifacts
 
 on:
+  # we build on PRs and develop to (hopefully) get early warning
+  # of things breaking (but only build one set of debs)
+  pull_request:
   push:
-    # we build on develop and release branches to (hopefully) get early warning
-    # of things breaking
-    branches: ["develop", "release-*"]
+    branches: ["develop"]
 
-    # we also rebuild on tags, so that we can be sure of picking the artifacts
-    # from the right tag.
+    # we do the full build on tags.
     tags: ["v*"]
 
 permissions:
   contents: write
 
 jobs:
-  # first get the list of distros to build for.
   get-distros:
+    name: "Calculate list of debian distros"
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v2
       - id: set-distros
         run: |
-          echo "::set-output name=distros::$(scripts-dev/build_debian_packages --show-dists-json)"
+          # if we're running from a tag, get the full list of distros; otherwise just use debian:sid
+          dists='["debian:sid"]'
+          if [[ $GITHUB_REF == refs/tags/* ]]; then
+              dists=$(scripts-dev/build_debian_packages --show-dists-json)
+          fi
+          echo "::set-output name=distros::$dists"
     # map the step outputs to job outputs
     outputs:
       distros: ${{ steps.set-distros.outputs.distros }}
@@ -66,7 +71,7 @@ jobs:
   # if it's a tag, create a release and attach the artifacts to it
   attach-assets:
     name: "Attach assets to release"
-    if: startsWith(github.ref, 'refs/tags/')
+    if: ${{ !failure() && !cancelled() && startsWith(github.ref, 'refs/tags/') }}
     needs:
       - build-debs
       - build-sdist
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index bf36ee1cdf..505bac1308 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -65,14 +65,14 @@ jobs:
 
   # Dummy step to gate other tests on without repeating the whole list
   linting-done:
-    if: ${{ always() }} # Run this even if prior jobs were skipped
+    if: ${{ !cancelled() }} # Run this even if prior jobs were skipped
     needs: [lint, lint-crlf, lint-newsfile, lint-sdist]
     runs-on: ubuntu-latest
     steps:
       - run: "true"
 
   trial:
-    if: ${{ !failure() }} # Allow previous steps to be skipped, but not fail
+    if: ${{ !cancelled() && !failure() }} # Allow previous steps to be skipped, but not fail
     needs: linting-done
     runs-on: ubuntu-latest
     strategy:
@@ -131,7 +131,7 @@ jobs:
           || true
 
   trial-olddeps:
-    if: ${{ !failure() }} # Allow previous steps to be skipped, but not fail
+    if: ${{ !cancelled() && !failure() }} # Allow previous steps to be skipped, but not fail
     needs: linting-done
     runs-on: ubuntu-latest
     steps:
@@ -156,7 +156,7 @@ jobs:
 
   trial-pypy:
     # Very slow; only run if the branch name includes 'pypy'
-    if: ${{ contains(github.ref, 'pypy') && !failure() }}
+    if: ${{ contains(github.ref, 'pypy') && !failure() && !cancelled() }}
     needs: linting-done
     runs-on: ubuntu-latest
     strategy:
@@ -185,7 +185,7 @@ jobs:
           || true
 
   sytest:
-    if: ${{ !failure() }}
+    if: ${{ !failure() && !cancelled() }}
     needs: linting-done
     runs-on: ubuntu-latest
     container:
@@ -245,7 +245,7 @@ jobs:
             /logs/**/*.log*
 
   portdb:
-    if: ${{ !failure() }} # Allow previous steps to be skipped, but not fail
+    if: ${{ !failure() && !cancelled() }} # Allow previous steps to be skipped, but not fail
     needs: linting-done
     runs-on: ubuntu-latest
     strategy:
@@ -286,7 +286,7 @@ jobs:
       - run: .buildkite/scripts/test_synapse_port_db.sh
 
   complement:
-    if: ${{ !failure() }}
+    if: ${{ !failure() && !cancelled() }}
     needs: linting-done
     runs-on: ubuntu-latest
     container:
diff --git a/changelog.d/10383.misc b/changelog.d/10383.misc
new file mode 100644
index 0000000000..952c1e77a8
--- /dev/null
+++ b/changelog.d/10383.misc
@@ -0,0 +1 @@
+Make the Github Actions workflow configuration more efficient.