diff --git a/.circleci/config.yml b/.circleci/config.yml
deleted file mode 100644
index d0914df3de..0000000000
--- a/.circleci/config.yml
+++ /dev/null
@@ -1,109 +0,0 @@
-# We use CircleCI to run a basic test for arm64.
-#
-# To reduce the complexity, we let this test verify our built images works with
-# arm64, but doesn't test the acquisition of HTTPS certificates (because it
-# requires a ACME server) or enforcement of the chart's NetworkPolicy resources
-# (because it requires Calico or similar to do it robustly).
-#
-version: 2.1
-
-orbs:
-  python: circleci/python@2.1.1
-
-jobs:
-  # Testing on arm64
-  # https://circleci.com/docs/using-arm/#using-arm-resources
-  test-arm:
-    machine:
-      image: ubuntu-2204:current
-    resource_class: arm.medium
-    steps:
-      - checkout
-
-      # The k3s setup should be kept similar to how we do it in
-      # https://github.com/jupyterhub/action-k3s-helm.
-      - run:
-          name: Setup k3s
-          command: >-
-            curl -sfL https://get.k3s.io |
-            INSTALL_K3S_CHANNEL=latest sh -s -
-            --disable metrics-server
-            --disable traefik
-            --disable-network-policy
-            --docker
-            --egress-selector-mode=disabled
-
-      - run:
-          name: Prepare a kubeconfig in ~/.kube/config
-          command: |
-            mkdir -p ~/.kube
-            sudo cat /etc/rancher/k3s/k3s.yaml > "$HOME/.kube/config"
-            chmod 600 "$HOME/.kube/config"
-
-      - run:
-          name: Install dependencies
-          command: |
-            . ci/common
-            setup_helm
-            pip3 install --no-cache-dir -r dev-requirements.txt
-
-      - run:
-          name: Run chartpress
-          command: |
-            export DOCKER_BUILDKIT=1
-            chartpress
-
-      - run:
-          name: Install local chart
-          command: |
-            export KUBECONFIG="$HOME/.kube/config"
-            helm upgrade --install jupyterhub ./jupyterhub \
-                --wait \
-                --values dev-config.yaml \
-                --values dev-config-arm.yaml \
-                --values dev-config-local-chart-extra-config.yaml
-
-      - run:
-          name: Run tests
-          command: |
-            export KUBECONFIG="$HOME/.kube/config"
-            export HUB_URL=http://localhost:30080
-            . ./ci/common
-            # Print out logs & definition info from all pods if the tests fail
-            pytest --verbose --color=yes ./tests -m 'not netpol' || \
-               kubectl get pod -o name | \
-               xargs -I {} /bin/bash -c \
-                "echo Logs for {} && \
-                 kubectl get {} -o yaml && \
-                 kubectl describe {} && \
-                 kubectl logs --all-containers {} && \
-                 echo --------------------------------"
-
-      - run:
-          name: k3s.service status
-          when: on_fail
-          command: |
-            systemctl status --no-pager --full k3s.service || true
-
-      - run:
-          name: k3s.service logs
-          when: on_fail
-          command: |
-            journalctl --no-pager -xu k3s.service
-
-      - run:
-          name: k8s namespace report
-          when: on_fail
-          environment:
-            NAMESPACE: ""
-            POD_SELECTOR: ""
-            IMPORTANT_WORKLOADS: ""
-          command: |
-            export KUBECONFIG="$HOME/.kube/config"
-            wget https://raw.githubusercontent.com/jupyterhub/action-k8s-namespace-report/v1.1.0/k8s-namespace-report
-            bash k8s-namespace-report
-
-workflows:
-  main:
-    jobs:
-      - test-arm
diff --git a/.github/workflows/test-chart.yaml b/.github/workflows/test-chart.yaml
index 57a2b6478c..c2abdfbfb1 100644
--- a/.github/workflows/test-chart.yaml
+++ b/.github/workflows/test-chart.yaml
@@ -114,7 +114,6 @@ jobs:
         continue-on-error: true
 
   test:
-    runs-on: ubuntu-24.04
     timeout-minutes: 20
 
     strategy:
@@ -131,12 +130,15 @@ jobs:
         include:
           - k3s-channel: latest
             test: install
+            # Also test arm64
+            os: ubuntu-24.04-arm
           - k3s-channel: stable # also test hub-slim, and prePuller.hook
             test: install
             local-chart-extra-args: >-
               --set hub.image.name=quay.io/jupyterhub/k8s-hub-slim
               --set prePuller.hook.enabled=true
               --set prePuller.hook.pullOnlyOnChanges=true
+            os: ubuntu-24.04
           - k3s-channel: v1.31 # also test hub.existingSecret and subdomain_host
             test: install
             local-chart-extra-args: >-
@@ -146,6 +148,7 @@ jobs:
               --set hub.config.CryptKeeper.keys[0]=cccc3333
               --set hub.config.JupyterHub.subdomain_host=jupyterhub.example.org
             create-k8s-test-resources: true
+            os: ubuntu-24.04
 
           # We run three upgrade tests where we first install an already released
           # Helm chart version and then upgrade to the version we are now
@@ -174,6 +177,7 @@ jobs:
               --set hub.db.type=sqlite-pvc
               --set singleuser.storage.type=dynamic
             create-k8s-test-resources: true
+            os: ubuntu-24.04
           - k3s-channel: v1.29
             test: upgrade
             upgrade-from: dev
@@ -184,6 +188,7 @@ jobs:
             local-chart-extra-args: >-
               --set hub.db.type=sqlite-pvc
               --set singleuser.storage.type=dynamic
+            os: ubuntu-24.04
           - k3s-channel: v1.28
             test: upgrade
             # We're testing hub.db.upgrade with PostgreSQL so this version must be old
@@ -212,6 +217,9 @@ jobs:
               --set audit.logConnections=true
               --set audit.logDisconnections=true
               --set audit.clientMinMessages=debug
+            os: ubuntu-24.04
+
+    runs-on: ${{ matrix.os }}
 
     steps:
       - uses: actions/checkout@v4
diff --git a/dev-config-arm.yaml b/dev-config-arm.yaml
deleted file mode 100644
index 68629665a9..0000000000
--- a/dev-config-arm.yaml
+++ /dev/null
@@ -1,4 +0,0 @@
-# Override some values in dev-config.yaml
-proxy:
-  https:
-    enabled: false