diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index e98a7808656f..9a0b044755af 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -248,6 +248,46 @@ jobs:
           git submodule update --init --recursive --jobs 7
           ./project/scripts/sbt "community-build/testOnly dotty.communitybuild.CommunityBuildTestB"
 
+  community_build_c:
+    runs-on: [self-hosted, Linux]
+    container:
+      image: lampepfl/dotty:2020-11-19
+      options: --cpu-shares 4096
+      volumes:
+        - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
+        - ${{ github.workspace }}/../../cache/ivy:/root/.ivy2/cache
+        - ${{ github.workspace }}/../../cache/general:/root/.cache
+    if: "github.event_name == 'schedule' && github.repository == 'lampepfl/dotty'
+         || github.event_name == 'push'
+         || (
+           github.event_name == 'pull_request'
+           && !contains(github.event.pull_request.body, '[skip ci]')
+           && !contains(github.event.pull_request.body, '[skip community_build]')
+         )
+         || (
+           github.event_name == 'workflow_dispatch'
+           && github.repository == 'lampepfl/dotty'
+         )"
+
+    steps:
+      - name: Checkout cleanup script
+        uses: actions/checkout@v2
+
+      - name: Cleanup
+        run: .github/workflows/cleanup.sh
+
+      - name: Git Checkout
+        uses: actions/checkout@v2
+
+      - name: Add SBT proxy repositories
+        run: cp -vf .github/workflows/repositories /root/.sbt/ ; true
+
+      - name: Test
+        run: |
+          git submodule sync
+          git submodule update --init --recursive --jobs 7
+          ./project/scripts/sbt "community-build/testOnly dotty.communitybuild.CommunityBuildTestC"
+
   test_sbt:
     runs-on: [self-hosted, Linux]
     container:
@@ -344,7 +384,7 @@ jobs:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
         - ${{ github.workspace }}/../../cache/ivy:/root/.ivy2/cache
         - ${{ github.workspace }}/../../cache/general:/root/.cache
-    needs: [test_non_bootstrapped, test, community_build_a, community_build_b, test_sbt, test_java8]
+    needs: [test_non_bootstrapped, test, community_build_a, community_build_b, community_build_c, test_sbt, test_java8]
     if: "(github.event_name == 'schedule' || github.event_name == 'workflow_dispatch') && github.repository == 'lampepfl/dotty'"
     env:
       NIGHTLYBUILD: yes
@@ -421,7 +461,7 @@ jobs:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
         - ${{ github.workspace }}/../../cache/ivy:/root/.ivy2/cache
         - ${{ github.workspace }}/../../cache/general:/root/.cache
-    needs: [test_non_bootstrapped, test, community_build_a, community_build_b, test_sbt, test_java8]
+    needs: [test_non_bootstrapped, test, community_build_a, community_build_b, community_build_c, test_sbt, test_java8]
     if: "github.event_name == 'push'
          && startsWith(github.event.ref, 'refs/tags/')
          && !startsWith(github.event.ref, 'refs/tags/sbt-dotty-')"
@@ -549,7 +589,7 @@ jobs:
         - ${{ github.workspace }}/../../cache/sbt:/root/.sbt
         - ${{ github.workspace }}/../../cache/ivy:/root/.ivy2/cache
         - ${{ github.workspace }}/../../cache/general:/root/.cache
-    needs: [community_build_a, community_build_b, test_sbt]
+    needs: [community_build_a, community_build_b, community_build_c, test_sbt]
     if: "github.event_name == 'push'
          && startsWith(github.event.ref, 'refs/tags/sbt-dotty-')"
 
diff --git a/community-build/test/scala/dotty/communitybuild/CommunityBuildTest.scala b/community-build/test/scala/dotty/communitybuild/CommunityBuildTest.scala
index bb22a7ef2679..9c056bdb9ac4 100644
--- a/community-build/test/scala/dotty/communitybuild/CommunityBuildTest.scala
+++ b/community-build/test/scala/dotty/communitybuild/CommunityBuildTest.scala
@@ -84,34 +84,14 @@ abstract class CommunityBuildTest:
   }
 end CommunityBuildTest
 
+class TestCategory
+
 @Category(Array(classOf[TestCategory]))
 class CommunityBuildTestA extends CommunityBuildTest:
-  @Test def akka = projects.akka.run()
-  @Test def endpoints4s = projects.endpoints4s.run()
-  @Test def fansi = projects.fansi.run()
-  @Test def fastparse = projects.fastparse.run()
-  @Test def geny = projects.geny.run()
   @Test def izumiReflect = projects.izumiReflect.run()
-  @Test def oslib = projects.oslib.run()
-  // @Test def oslibWatch = projects.oslibWatch.run()
-  @Test def pprint = projects.pprint.run()
-  @Test def requests = projects.requests.run()
-  @Test def scalacheck = projects.scalacheck.run()
-  @Test def scalaCollectionCompat = projects.scalaCollectionCompat.run()
-  @Test def scalaParallelCollections = projects.scalaParallelCollections.run()
+  @Test def scalaSTM = projects.scalaSTM.run()
   @Test def scalatest = projects.scalatest.run()
-  @Test def scalatestplusScalacheck = projects.scalatestplusScalacheck.run()
-  @Test def scalaz = projects.scalaz.run()
-  @Test def sourcecode = projects.sourcecode.run()
-  @Test def stdLib213 = projects.stdLib213.run()
-  @Test def ujson = projects.ujson.run()
-  @Test def upickle = projects.upickle.run()
-  @Test def utest = projects.utest.run()
-  @Test def zio = projects.zio.run()
-  @Test def protoquill = projects.protoquill.run()
-  @Test def onnxScala = projects.onnxScala.run()
-
-  // 'scala-stm' and 'Sciss/Lucre':
+  // 'Sciss/Lucre' dependencies:
   // @Test def scissEqual      = projects.scissEqual     .run()
   // @Test def scissFingerTree = projects.scissFingerTree.run()
   // @Test def scissLog        = projects.scissLog       .run()
@@ -120,15 +100,12 @@ class CommunityBuildTestA extends CommunityBuildTest:
   // @Test def scissSerial     = projects.scissSerial    .run()
   // @Test def scissAsyncFile  = projects.scissAsyncFile .run()
   // @Test def scissSpan       = projects.scissSpan      .run()
-  @Test def scalaSTM        = projects.scalaSTM       .run()
-  @Test def scissLucre      = projects.scissLucre     .run()
-
+  @Test def scissLucre = projects.scissLucre.run()
+  @Test def zio = projects.zio.run()
 end CommunityBuildTestA
 
 @Category(Array(classOf[TestCategory]))
 class CommunityBuildTestB extends CommunityBuildTest:
-  @Test def algebra = projects.algebra.run()
-  @Test def betterfiles = projects.betterfiles.run()
   @Test def cats = projects.cats.run()
   @Test def catsEffect2 = projects.catsEffect2.run()
   @Test def catsEffect3 = projects.catsEffect3.run()
@@ -137,26 +114,51 @@ class CommunityBuildTestB extends CommunityBuildTest:
   @Test def discipline = projects.discipline.run()
   @Test def disciplineMunit = projects.disciplineMunit.run()
   @Test def disciplineSpecs2 = projects.disciplineSpecs2.run()
+  @Test def munit = projects.munit.run()
+  @Test def perspective = projects.perspective.run()
+  @Test def scodec = projects.scodec.run()
+  @Test def scodecBits = projects.scodecBits.run()
+  @Test def simulacrumScalafixAnnotations = projects.simulacrumScalafixAnnotations.run()
+end CommunityBuildTestB
+
+@Category(Array(classOf[TestCategory]))
+class CommunityBuildTestC extends CommunityBuildTest:
+  @Test def akka = projects.akka.run()
+  @Test def algebra = projects.algebra.run()
+  @Test def betterfiles = projects.betterfiles.run()
+  @Test def cask = projects.cask.run()
   // Temporarily disabled until problem discovered in comments to #9449 is fixed
   // @Test def dottyCpsAsync = projects.dottyCpsAsync.run()
   @Test def effpi = projects.effpi.run()
+  @Test def endpoints4s = projects.endpoints4s.run()
+  @Test def fansi = projects.fansi.run()
+  @Test def fastparse = projects.fastparse.run()
+  @Test def geny = projects.geny.run()
   @Test def intent = projects.intent.run()
   @Test def minitest = projects.minitest.run()
-  @Test def munit = projects.munit.run()
-  @Test def scodec = projects.scodec.run()
-  @Test def scodecBits = projects.scodecBits.run()
+  @Test def onnxScala = projects.onnxScala.run()
+  @Test def oslib = projects.oslib.run()
+  // @Test def oslibWatch = projects.oslibWatch.run()
+  @Test def pprint = projects.pprint.run()
+  @Test def protoquill = projects.protoquill.run()
+  @Test def requests = projects.requests.run()
+  @Test def scalacheck = projects.scalacheck.run()
+  @Test def scalaCollectionCompat = projects.scalaCollectionCompat.run()
   @Test def scalap = projects.scalap.run()
+  @Test def scalaParallelCollections = projects.scalaParallelCollections.run()
   @Test def scalaParserCombinators = projects.scalaParserCombinators.run()
   @Test def scalaPB = projects.scalaPB.run()
+  @Test def scalatestplusScalacheck = projects.scalatestplusScalacheck.run()
   @Test def scalaXml = projects.scalaXml.run()
+  @Test def scalaz = projects.scalaz.run()
   @Test def scas = projects.scas.run()
   @Test def sconfig = projects.sconfig.run()
   @Test def shapeless = projects.shapeless.run()
-  @Test def simulacrumScalafixAnnotations = projects.simulacrumScalafixAnnotations.run()
+  @Test def sourcecode = projects.sourcecode.run()
+  @Test def stdLib213 = projects.stdLib213.run()
+  @Test def ujson = projects.ujson.run()
+  @Test def upickle = projects.upickle.run()
+  @Test def utest = projects.utest.run()
   @Test def verify = projects.verify.run()
   @Test def xmlInterpolator = projects.xmlInterpolator.run()
-  @Test def perspective = projects.perspective.run()
-
-end CommunityBuildTestB
-
-class TestCategory
+end CommunityBuildTestC