ci: switch to GitHub cache for all runners

diff --git a/.github/actions/configure-docker/action.yml b/.github/actions/configure-docker/action.yml
index b4abf7c2..6f89dc8b 100644
--- a/.github/actions/configure-docker/action.yml
+++ b/.github/actions/configure-docker/action.yml
@@ -1,27 +1,14 @@
 name: 'Configure Docker'
 description: 'Set up Docker build driver and configure build cache args'
-inputs:
-  cache-provider:
-    description: 'gha or cirrus cache provider'
-    required: true
 runs:
   using: 'composite'
   steps:
-    - name: Check inputs
-      shell: python
-      run: |
-        # We expect only gha or cirrus as inputs to cache-provider
-        if "${{ inputs.cache-provider }}" not in ("gha", "cirrus"):
-          print("::warning title=Unknown input to configure docker action::Provided value was ${{ inputs.cache-provider }}")
-
     - name: Set up Docker Buildx
       uses: docker/setup-buildx-action@v4
-      with:
-        # Use host network to allow access to cirrus gha cache running on the host
-        driver-opts: |
-          network=host
 
-    # This is required to allow buildkit to access the actions cache
+    # This is required when using the gha cache backend with a manual docker buildx invocation.
+    # Docker will check for variables $ACTIONS_CACHE_URL, $ACTIONS_RESULTS_URL and $ACTIONS_RUNTIME_TOKEN
+    # which are set automatically when running on GitHub infra: https://docs.docker.com/build/cache/backends/gha/#synopsis
     - name: Expose actions cache variables
       uses: actions/github-script@v8
       with:
@@ -37,24 +24,12 @@ runs:
       shell: bash
       run: |
         # Configure docker build cache backend
-        #
-        # On forks the gha cache will work but will use Github's cache backend.
-        # Docker will check for variables $ACTIONS_CACHE_URL, $ACTIONS_RESULTS_URL and $ACTIONS_RUNTIME_TOKEN
-        # which are set automatically when running on GitHub infra: https://docs.docker.com/build/cache/backends/gha/#synopsis
-
-        # Use cirrus cache host
-        if [[ ${{ inputs.cache-provider }} == 'cirrus' ]]; then
-          url_args="url=${CIRRUS_CACHE_HOST},url_v2=${CIRRUS_CACHE_HOST}"
-        else
-          url_args=""
-        fi
-
         # Always optimistically --cache‑from in case a cache blob exists
-        args=(--cache-from "type=gha${url_args:+,${url_args}},scope=${CONTAINER_NAME}")
+        args=(--cache-from "type=gha,scope=${CONTAINER_NAME}")
 
-        # Only add --cache-to when using the Cirrus cache provider and pushing to the default branch.
-        if [[ ${{ inputs.cache-provider }} == 'cirrus' && ${{ github.event_name }} == "push" && ${{ github.ref_name }} == ${{ github.event.repository.default_branch }} ]]; then
-          args+=(--cache-to "type=gha${url_args:+,${url_args}},mode=max,ignore-error=true,scope=${CONTAINER_NAME}")
+        # Only add --cache-to when pushing to the default branch.
+        if [[ ${{ github.event_name }} == "push" && ${{ github.ref_name }} == ${{ github.event.repository.default_branch }} ]]; then
+          args+=(--cache-to "type=gha,mode=max,ignore-error=true,scope=${CONTAINER_NAME}")
         fi
 
         # Always `--load` into docker images (needed when using the `docker-container` build driver).
diff --git a/.github/actions/restore-caches/action.yml b/.github/actions/restore-caches/action.yml
index 21f2807f..ee07d68b 100644
--- a/.github/actions/restore-caches/action.yml
+++ b/.github/actions/restore-caches/action.yml
@@ -5,7 +5,7 @@ runs:
   steps:
     - name: Restore Ccache cache
       id: ccache-cache
-      uses: cirruslabs/cache/restore@v5
+      uses: actions/cache/restore@v5
       with:
         path: ${{ env.CCACHE_DIR }}
         key: ccache-${{ env.CONTAINER_NAME }}-${{ github.run_id }}
@@ -14,7 +14,7 @@ runs:
 
     - name: Restore depends sources cache
       id: depends-sources
-      uses: cirruslabs/cache/restore@v5
+      uses: actions/cache/restore@v5
       with:
         path: ${{ env.SOURCES_PATH }}
         key: depends-sources-${{ env.CONTAINER_NAME }}-${{ env.DEPENDS_HASH }}
@@ -23,7 +23,7 @@ runs:
 
     - name: Restore built depends cache
       id: depends-built
-      uses: cirruslabs/cache/restore@v5
+      uses: actions/cache/restore@v5
       with:
         path: ${{ env.BASE_CACHE }}
         key: depends-built-${{ env.CONTAINER_NAME }}-${{ env.DEPENDS_HASH }}
@@ -32,7 +32,7 @@ runs:
 
     - name: Restore previous releases cache
       id: previous-releases
-      uses: cirruslabs/cache/restore@v5
+      uses: actions/cache/restore@v5
       with:
         path: ${{ env.PREVIOUS_RELEASES_DIR }}
         key: previous-releases-${{ env.CONTAINER_NAME }}-${{ env.PREVIOUS_RELEASES_HASH }}
diff --git a/.github/actions/save-caches/action.yml b/.github/actions/save-caches/action.yml
index 3072ab3f..8667c914 100644
--- a/.github/actions/save-caches/action.yml
+++ b/.github/actions/save-caches/action.yml
@@ -11,28 +11,28 @@ runs:
         echo "previous releases direct cache hit to primary key: ${{ env.previous-releases-cache-hit }}"
 
     - name: Save Ccache cache
-      uses: cirruslabs/cache/save@v5
+      uses: actions/cache/save@v5
       if: ${{ (github.event_name == 'push') && (github.ref_name == github.event.repository.default_branch) }}
       with:
         path: ${{ env.CCACHE_DIR }}
         key: ccache-${{ env.CONTAINER_NAME }}-${{ github.run_id }}
 
     - name: Save depends sources cache
-      uses: cirruslabs/cache/save@v5
+      uses: actions/cache/save@v5
       if: ${{ (github.event_name == 'push') && (github.ref_name == github.event.repository.default_branch) && (env.depends-sources-cache-hit != 'true') }}
       with:
         path: ${{ env.SOURCES_PATH }}
         key: depends-sources-${{ env.CONTAINER_NAME }}-${{ env.DEPENDS_HASH }}
 
     - name: Save built depends cache
-      uses: cirruslabs/cache/save@v5
+      uses: actions/cache/save@v5
       if: ${{ (github.event_name == 'push') && (github.ref_name == github.event.repository.default_branch) && (env.depends-built-cache-hit != 'true' )}}
       with:
         path: ${{ env.BASE_CACHE }}
         key: depends-built-${{ env.CONTAINER_NAME }}-${{ env.DEPENDS_HASH }}
 
     - name: Save previous releases cache
-      uses: cirruslabs/cache/save@v5
+      uses: actions/cache/save@v5
       if: ${{ (github.event_name == 'push') && (github.ref_name == github.event.repository.default_branch) && (env.previous-releases-cache-hit != 'true' )}}
       with:
         path: ${{ env.PREVIOUS_RELEASES_DIR }}
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index ea62ef28..9c78c10d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -19,8 +19,7 @@ concurrency:
 
 env:
   CI_FAILFAST_TEST_LEAVE_DANGLING: 1  # GHA does not care about dangling processes and setting this variable avoids killing the CI script itself on error
-  CIRRUS_CACHE_HOST: http://127.0.0.1:12321/ # When using Cirrus Runners this host can be used by the docker `gha` build cache type.
-  REPO_USE_CIRRUS_RUNNERS: 'bitcoin/bitcoin' # Use cirrus runners and cache for this repo, instead of falling back to the slow GHA runners
+  REPO_USE_CIRRUS_RUNNERS: 'bitcoin/bitcoin' # Use cirrus runners for this repo, instead of falling back to the slow GHA runners
 
 defaults:
   run:
@@ -60,7 +59,7 @@ jobs:
     needs: runners
     runs-on: ${{ needs.runners.outputs.provider == 'cirrus' && 'ghcr.io/cirruslabs/ubuntu-runner-amd64:24.04-md' || 'ubuntu-24.04' }}
     env:
-      TEST_RUNNER_PORT_MIN: "14000"  # Use a larger port, to avoid colliding with CIRRUS_CACHE_HOST port 12321.
+      TEST_RUNNER_PORT_MIN: "14000"  # Use a larger port range to avoid colliding with other CI services.
     if: github.event_name == 'pull_request' && github.event.pull_request.commits != 1
     timeout-minutes: 360  # Use maximum time, see https://docs.github.com/en/actions/writing-workflows/workflow-syntax-for-github-actions#jobsjob_idtimeout-minutes.
     steps:
@@ -361,8 +360,6 @@ jobs:
 
       - name: Configure Docker
         uses: ./.github/actions/configure-docker
-        with:
-          cache-provider: ${{ needs.runners.outputs.provider }}
 
       - name: CI script
         run: ./ci/test_run_all.sh
@@ -553,8 +550,6 @@ jobs:
 
       - name: Configure Docker
         uses: ./.github/actions/configure-docker
-        with:
-          cache-provider: ${{ matrix.provider || needs.runners.outputs.provider }}
 
       - name: Clear unnecessary files
         if: ${{ needs.runners.outputs.provider == 'gha' && true || false }} # Only needed on GHA runners
@@ -596,8 +591,6 @@ jobs:
 
       - name: Configure Docker
         uses: ./.github/actions/configure-docker
-        with:
-          cache-provider: ${{ needs.runners.outputs.provider }}
 
       - name: CI script
         run: |
diff --git a/ci/README.md b/ci/README.md
index 293294a5..0f43b4f1 100644
--- a/ci/README.md
+++ b/ci/README.md
@@ -85,15 +85,15 @@ To configure the primary repository, follow these steps:
 3. Enable organisation-level runners to be used in public repositories:
    1. `Org settings -> Actions -> Runner Groups -> Default -> Allow public repos`
 4. Permit the following actions to run:
-   1. cirruslabs/cache/restore@\*
-   1. cirruslabs/cache/save@\*
+   1. actions/cache/restore@\*
+   1. actions/cache/save@\*
    1. docker/setup-buildx-action@\*
    1. actions/github-script@\*
 
 ### Forked repositories
 
 When used in a fork the CI will run on GitHub's free hosted runners by default.
-In this case, due to GitHub's 10GB-per-repo cache size limitations caches will be frequently evicted and missed, but the workflows will run (slowly).
+In this case, GitHub's cache size limitations may cause caches to be frequently evicted and missed, but the workflows will run (slowly).
 
 It is also possible to use your own Cirrus Runners in your own fork with an appropriate patch to the `REPO_USE_CIRRUS_RUNNERS` variable in ../.github/workflows/ci.yml
 NB that Cirrus Runners only work at an organisation level, therefore in order to use your own Cirrus Runners, *the fork must be within your own organisation*.