diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index c173d6b27..94e40d510 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -66,14 +66,15 @@ jobs:
         max-depth: 3
 
   cmake-version:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     steps:
     - uses: actions/checkout@v2
       with:
         submodules: true
     - name: Bootstrap
       run: |
-        sudo pip3 install --system -U cmake==3.10.3
+        sudo pip3 install -U scikit-build
+        sudo pip3 install -U cmake==3.10.3
         cmake --version | grep 3.10.3
         sudo apt-get --no-install-recommends install -y ninja-build libreadline-dev libncurses-dev
     - name: Build
@@ -123,7 +124,7 @@ jobs:
         script/check-scan-build
 
   mbedtls3-build:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     steps:
     - uses: actions/checkout@v2
       with:
@@ -143,7 +144,7 @@ jobs:
 
   arm-gcc:
     name: arm-gcc-${{ matrix.gcc_ver }}
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     strategy:
       fail-fast: false
       matrix:
@@ -175,7 +176,8 @@ jobs:
         wget --tries 4 --no-check-certificate --quiet ${{ matrix.gcc_download_url }} -O gcc-arm.tar.bz2
         tar xjf gcc-arm.tar.bz2
         # use the minimal required cmake version
-        sudo pip3 install --system -U cmake==3.10.3
+        sudo pip3 install -U scikit-build
+        sudo pip3 install -U cmake==3.10.3
         cmake --version | grep 3.10.3
     - name: Build
       run: |
@@ -184,11 +186,11 @@ jobs:
 
   gcc:
     name: gcc-${{ matrix.gcc_ver }}
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     strategy:
       fail-fast: false
       matrix:
-        gcc_ver: [5, 6, 7, 8, 9, 10, 11]
+        gcc_ver: [7, 8, 9, 10, 11]
     env:
       CC: gcc-${{ matrix.gcc_ver }}
       CXX: g++-${{ matrix.gcc_ver }}
diff --git a/.github/workflows/posix.yml b/.github/workflows/posix.yml
index 2ec9fa574..3776b11e1 100644
--- a/.github/workflows/posix.yml
+++ b/.github/workflows/posix.yml
@@ -41,7 +41,7 @@ jobs:
       if: "github.ref != 'refs/heads/main'"
 
   expects-linux:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     env:
       CFLAGS: -DCLI_COAP_SECURE_USE_COAP_DEFAULT_HANDLER=1 -DOPENTHREAD_CONFIG_MLE_MAX_CHILDREN=15
       CXXFLAGS: -DCLI_COAP_SECURE_USE_COAP_DEFAULT_HANDLER=1 -DOPENTHREAD_CONFIG_MLE_MAX_CHILDREN=15
@@ -77,12 +77,11 @@ jobs:
     - name: Run TUN Mode
       run: |
         sudo rm /etc/apt/sources.list.d/* && sudo apt-get update
-        sudo apt-get install --no-install-recommends -y dnsmasq bind9-host ntp
-        sudo systemctl start dnsmasq ntp
-        host ipv6.google.com 127.0.0.1
-        echo 'listen-address=::1' | sudo tee /etc/dnsmasq.conf
         echo 0 | sudo tee /proc/sys/net/ipv6/conf/all/disable_ipv6
-        sudo systemctl restart dnsmasq
+        sudo apt-get install --no-install-recommends -y bind9-host ntp socat
+        sudo systemctl restart ntp
+        sudo socat 'UDP6-LISTEN:53,fork,reuseaddr,bind=[::1]' UDP:127.0.0.53:53 &
+        host ipv6.google.com 127.0.0.53
         host ipv6.google.com ::1
         ulimit -c unlimited
         ./script/test prepare_coredump_upload
diff --git a/.github/workflows/simulation-1.1.yml b/.github/workflows/simulation-1.1.yml
index 3754c9d3c..3fadd17aa 100644
--- a/.github/workflows/simulation-1.1.yml
+++ b/.github/workflows/simulation-1.1.yml
@@ -233,7 +233,7 @@ jobs:
         path: tmp/coverage.info
 
   expects:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     env:
       CFLAGS: -DCLI_COAP_SECURE_USE_COAP_DEFAULT_HANDLER=1 -DOPENTHREAD_CONFIG_MLE_MAX_CHILDREN=15
       CXXFLAGS: -DCLI_COAP_SECURE_USE_COAP_DEFAULT_HANDLER=1 -DOPENTHREAD_CONFIG_MLE_MAX_CHILDREN=15
diff --git a/.github/workflows/toranj.yml b/.github/workflows/toranj.yml
index 221913fde..8af954d8b 100644
--- a/.github/workflows/toranj.yml
+++ b/.github/workflows/toranj.yml
@@ -42,7 +42,7 @@ jobs:
 
   toranj-ncp:
     name: toranj-ncp-${{ matrix.TORANJ_RADIO }}
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     strategy:
       fail-fast: false
       matrix:
@@ -61,12 +61,15 @@ jobs:
         sudo rm /etc/apt/sources.list.d/* && sudo apt-get update
         sudo apt-get --no-install-recommends install -y dbus libdbus-1-dev
         sudo apt-get --no-install-recommends install -y autoconf-archive
-        sudo apt-get --no-install-recommends install -y bsdtar
+        sudo apt-get --no-install-recommends install -y libarchive-tools
         sudo apt-get --no-install-recommends install -y libtool
         sudo apt-get --no-install-recommends install -y libglib2.0-dev
-        sudo apt-get --no-install-recommends install -y libboost-dev libboost-signals-dev
         sudo apt-get --no-install-recommends install -y lcov
 
+        sudo add-apt-repository universe
+        sudo apt-get update
+        sudo apt-get --no-install-recommends install -y libboost-all-dev python2
+
         script/git-tool clone --depth=1 --branch=master https://github.com/openthread/wpantund.git
         cd wpantund
         ./bootstrap.sh
@@ -88,7 +91,7 @@ jobs:
 
   toranj-cli:
     name: toranj-cli-${{ matrix.TORANJ_RADIO }}
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     strategy:
       matrix:
         TORANJ_RADIO: ['15.4']
@@ -124,7 +127,7 @@ jobs:
     needs:
     - toranj-ncp
     - toranj-cli
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     steps:
     - uses: actions/checkout@v2
       with:
diff --git a/tests/toranj/start.sh b/tests/toranj/start.sh
index 3831afc2b..a7a7ebfc9 100755
--- a/tests/toranj/start.sh
+++ b/tests/toranj/start.sh
@@ -107,7 +107,7 @@ if [ "$TORANJ_CLI" = 1 ]; then
     log_file_name="ot-logs"
 else
     app_name="ncp"
-    python_app="python"
+    python_app="python2"
     log_file_name="wpantund-logs"
 fi