diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 914a3b51..6b1f65a2 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -21,7 +21,6 @@ jobs:
             buildtype: "boost"
             packages: ""
             packages_to_remove: ""
-            os: "ubuntu-20.04"
             container: "ubuntu:16.04"
             cxx: "g++"
             sources: ""
@@ -34,7 +33,6 @@ jobs:
             buildtype: "boost"
             packages: "g++-5"
             packages_to_remove: ""
-            os: "ubuntu-20.04"
             container: "ubuntu:16.04"
             cxx: "g++-5"
             sources: ""
@@ -47,7 +45,6 @@ jobs:
             buildtype: "boost"
             packages: "g++-6"
             packages_to_remove: ""
-            os: "ubuntu-20.04"
             container: "ubuntu:16.04"
             cxx: "g++-6"
             sources: ""
@@ -60,7 +57,6 @@ jobs:
             buildtype: "boost"
             packages: "g++-7"
             packages_to_remove: ""
-            os: "ubuntu-20.04"
             container: "ubuntu:16.04"
             cxx: "g++-7"
             sources: ""
@@ -71,9 +67,9 @@ jobs:
             cxxstd: "11,14,17"
           - name: "TOOLSET=clang COMPILER=clang++ CXXSTD=11 Job 4"
             buildtype: "boost"
-            packages: ""
+            packages: "clang"
             packages_to_remove: ""
-            os: "ubuntu-18.04"
+            container: "ubuntu:18.04"
             cxx: "clang++"
             sources: ""
             llvm_os: ""
@@ -85,7 +81,6 @@ jobs:
             buildtype: "boost"
             packages: "clang-4.0 libstdc++-6-dev"
             packages_to_remove: ""
-            os: "ubuntu-20.04"
             container: "ubuntu:16.04"
             cxx: "clang++-4.0"
             sources: ""
@@ -98,7 +93,6 @@ jobs:
             buildtype: "boost"
             packages: "clang-5.0 libstdc++-7-dev"
             packages_to_remove: ""
-            os: "ubuntu-20.04"
             container: "ubuntu:16.04"
             cxx: "clang++-5.0"
             sources: ""
@@ -108,7 +102,7 @@ jobs:
             compiler: "clang++-5.0"
             cxxstd: "11,14,1z"
 
-    runs-on: ${{ matrix.os }}
+    runs-on: ${{ matrix.os || 'ubuntu-latest' }}
     container: ${{ matrix.container }}
 
     steps:
@@ -121,10 +115,6 @@ jobs:
             apt-get -o Acquire::Retries=3 update && DEBIAN_FRONTEND=noninteractive apt-get -y install tzdata && apt-get -o Acquire::Retries=3 install -y sudo software-properties-common wget curl apt-transport-https make apt-file sudo unzip libssl-dev build-essential autotools-dev autoconf automake g++ libc++-helpers python ruby cpio gcc-multilib g++-multilib pkgconf python3 ccache libpython-dev
             sudo apt-add-repository ppa:git-core/ppa
             sudo apt-get -o Acquire::Retries=3 update && apt-get -o Acquire::Retries=3 -y install git
-            python_version=$(python3 -c 'import sys; print("{0.major}.{0.minor}".format(sys.version_info))')
-            sudo wget https://bootstrap.pypa.io/pip/$python_version/get-pip.py
-            sudo python3 get-pip.py
-            sudo /usr/local/bin/pip install cmake
 
       - uses: actions/checkout@v2