diff --git a/.appveyor.yml b/.appveyor.yml
index 72b790d7..6df0cd1d 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -18,7 +18,7 @@ install:
 build_script:
     - git submodule update --init
     - mkdir build
-    - c:\cygwin-root\bin\sh -lc "cd $APPVEYOR_BUILD_FOLDER/build; ../configure --enable-charset --enable-zlib --enable-openssl --enable-perl --enable-python --enable-cyrus --enable-argon < /dev/null; result=$?; cmake --system-information > config.log; appveyor PushArtifact config.log; exit $result"
+    - c:\cygwin-root\bin\sh -lc "cd $APPVEYOR_BUILD_FOLDER/build; env ZNC_QT_VER=5 ../configure --enable-charset --enable-zlib --enable-openssl --enable-perl --enable-python --enable-cyrus --enable-argon < /dev/null; result=$?; cmake --system-information > config.log; appveyor PushArtifact config.log; exit $result"
     - c:\cygwin-root\bin\sh -lc "cd $APPVEYOR_BUILD_FOLDER/build; make VERBOSE=1 -j2 < /dev/null"
     - c:\cygwin-root\bin\sh -lc "cd $APPVEYOR_BUILD_FOLDER/build; make install < /dev/null"
     - c:\cygwin-root\bin\sh -lc "znc --version"
@@ -27,4 +27,4 @@ build_script:
     - c:\cygwin-root\bin\sh -lc "rebase -s -v $(cat /tmp/files-to-rebase)"
 test_script:
     - c:\cygwin-root\bin\sh -lc "cd $APPVEYOR_BUILD_FOLDER/build; make VERBOSE=1 unittest < /dev/null"
-    - c:\cygwin-root\bin\sh -lc "cd $APPVEYOR_BUILD_FOLDER/build; make VERBOSE=1 inttest < /dev/null"
+    - c:\cygwin-root\bin\sh -lc "cd $APPVEYOR_BUILD_FOLDER/build; env ZNC_QT_VER=5 make VERBOSE=1 inttest < /dev/null"
diff --git a/.github/build.sh b/.github/build.sh
index 14214901..33a56ed3 100644
--- a/.github/build.sh
+++ b/.github/build.sh
@@ -6,7 +6,7 @@ ls -la
 cpanm --local-lib=~/perl5 local::lib
 eval $(perl -I ~/perl5/lib/perl5/ -Mlocal::lib)
 cpanm --notest Devel::Cover::Report::Clover
-pip3 install --user coverage
+pip3 install --user --break-system-packages coverage
 export ZNC_MODPERL_COVERAGE=1
 #export ZNC_MODPYTHON_COVERAGE=1
 
@@ -39,7 +39,7 @@ ls -lRa
 
 case "${CC:-gcc}" in
 	gcc)
-		lcov --directory . --capture --output-file lcov-coverage.txt
+		lcov --directory . --capture --output-file lcov-coverage.txt --ignore-errors mismatch
 		lcov --list lcov-coverage.txt
 		;;
 	clang)
diff --git a/.github/ubuntu_deps.sh b/.github/ubuntu_deps.sh
index 2e6d12b2..bc0bec58 100644
--- a/.github/ubuntu_deps.sh
+++ b/.github/ubuntu_deps.sh
@@ -1,4 +1,4 @@
 sudo apt-get update
-sudo apt-get install -y tcl-dev libsasl2-dev libicu-dev swig qtbase5-dev libboost-locale-dev libperl-dev libargon2-dev cpanminus gettext clang llvm lcov
+sudo apt-get install -y tcl-dev libsasl2-dev libicu-dev swig qt6-base-dev libboost-locale-dev libperl-dev libargon2-dev cpanminus gettext clang llvm lcov
 sudo apt-get upgrade -y
 
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 007bf287..07090ea9 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -6,7 +6,7 @@ on:
 jobs:
   gcc:
     name: GCC
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     steps:
       - uses: actions/checkout@v4
         with:
@@ -23,7 +23,7 @@ jobs:
 
   tarball:
     name: Tarball
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     steps:
       - uses: actions/checkout@v4
         with:
@@ -48,7 +48,7 @@ jobs:
   # can be removed when asan below is fixed
   clang:
     name: Clang
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     env:
       CXX: clang++
       CC: clang
@@ -69,7 +69,7 @@ jobs:
  
   #clang_asan:
     #name: Clang ASAN
-    #runs-on: ubuntu-20.04
+    #runs-on: ubuntu-24.04
     #env:
       #CXX: clang++
       #CC: clang
@@ -85,7 +85,7 @@ jobs:
 
   #clang_tsan:
     #name: Clang TSAN
-    #runs-on: ubuntu-20.04
+    #runs-on: ubuntu-24.04
     #env:
       #CXX: clang++
       #CC: clang
@@ -119,7 +119,7 @@ jobs:
           submodules: true
       - run: |
           brew update
-          brew install icu4c qt5 gettext pkg-config cpanminus boost
+          brew install icu4c qt6 gettext pkg-config cpanminus boost argon2 swig
       - run: source .github/build.sh
       - uses: codecov/codecov-action@v3
 
diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index d00529a9..5b72f88b 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -2,7 +2,7 @@ name: "CodeQL"
 
 on:
   push:
-    branches: [ 'master', '1.6.x' ]
+    branches: [ 'master', '1.9.x' ]
   pull_request:
     # The branches below must be a subset of the branches above
     branches: [ 'master' ]
@@ -12,7 +12,7 @@ on:
 jobs:
   analyze:
     name: Analyze
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     permissions:
       actions: read
       contents: read
@@ -28,7 +28,10 @@ jobs:
       uses: actions/checkout@v4
       with:
         submodules: true
-    - run: source .github/ubuntu_deps.sh
+    - run: |
+        source .github/ubuntu_deps.sh
+        sudo apt-get remove -y qt6-base-dev
+        sudo apt-get install -y qtbase5-dev
       
     - name: Initialize CodeQL
       uses: github/codeql-action/init@v3
@@ -36,6 +39,8 @@ jobs:
         languages: ${{ matrix.language }}
 
     - run: source .github/build.sh
+      env:
+        ZNC_QT_VER: "5"
 
     - name: Perform CodeQL Analysis
       uses: github/codeql-action/analyze@v3
diff --git a/cmake/use_homebrew.cmake b/cmake/use_homebrew.cmake
index 52e0270a..547b860e 100644
--- a/cmake/use_homebrew.cmake
+++ b/cmake/use_homebrew.cmake
@@ -54,12 +54,17 @@ if(brew_python_f EQUAL 0)
 		"${brew_python}/Frameworks/Python.framework")
 endif()
 
-execute_process(COMMAND "${brew}" --prefix qt5
-	RESULT_VARIABLE brew_qt5_f
-	OUTPUT_VARIABLE brew_qt5 OUTPUT_STRIP_TRAILING_WHITESPACE ERROR_QUIET)
-if(brew_qt5_f EQUAL 0)
-	find_package_message(brew_qt5 "Qt5 via Homebrew: ${brew_qt5}"
-		"${brew_qt5}")
+if(DEFINED ENV{ZNC_QT_VER})
+	set(ZNC_QT_VER $ENV{ZNC_QT_VER})
+else()
+	set(ZNC_QT_VER 6)
+endif()
+execute_process(COMMAND "${brew}" --prefix qt${ZNC_QT_VER}
+	RESULT_VARIABLE brew_qt_f
+	OUTPUT_VARIABLE brew_qt OUTPUT_STRIP_TRAILING_WHITESPACE ERROR_QUIET)
+if(brew_qt_f EQUAL 0)
+	find_package_message(brew_qt "Qt via Homebrew: ${brew_qt}"
+		"${brew_qt}")
 endif()
 
 execute_process(COMMAND "${brew}" --prefix gettext
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index a13cbdb0..da9ed54f 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -90,7 +90,7 @@ externalproject_add(inttest_bin
 	"-DGTEST_ROOT:path=${GTEST_ROOT}"
 	"-DGMOCK_ROOT:path=${GMOCK_ROOT}"
 	"-DZNC_BIN_DIR:path=${CMAKE_INSTALL_FULL_BINDIR}"
-	"-DQt5_HINTS:path=${brew_qt5}")
+	"-DQt_HINTS:path=${brew_qt}")
 add_custom_target(inttest COMMAND
 	#   MAKEFLAGS:
 	# Prevent a warning from test of znc-buildmod, when inner make
diff --git a/test/integration/CMakeLists.txt b/test/integration/CMakeLists.txt
index 62a70ada..e1c0653f 100644
--- a/test/integration/CMakeLists.txt
+++ b/test/integration/CMakeLists.txt
@@ -24,7 +24,13 @@ set(CMAKE_THREAD_PREFER_PTHREAD true)
 set(THREADS_PREFER_PTHREAD_FLAG true)
 find_package(Threads REQUIRED)
 
-find_package(Qt5Network 5.4 REQUIRED HINTS ${Qt5_HINTS})
+if(DEFINED ENV{ZNC_QT_VER})
+	set(ZNC_QT_VER $ENV{ZNC_QT_VER})
+else()
+	set(ZNC_QT_VER 6)
+endif()
+
+find_package(Qt${ZNC_QT_VER}Network 5.4 REQUIRED HINTS ${Qt_HINTS})
 
 # Force the simple internal regex engine to get consistent behavior on all
 # platforms. See
@@ -42,7 +48,7 @@ add_executable(inttest
 	"${GTEST_ROOT}/src/gtest-all.cc"
 	"${GMOCK_ROOT}/src/gmock-all.cc")
 
-target_link_libraries(inttest Qt5::Network Threads::Threads)
+target_link_libraries(inttest Qt${ZNC_QT_VER}::Network Threads::Threads)
 target_include_directories(inttest PUBLIC
 	"${PROJECT_SOURCE_DIR}/framework"
 	"${PROJECT_BINARY_DIR}"
diff --git a/test/integration/framework/znctest.cpp b/test/integration/framework/znctest.cpp
index 1b81db6a..7cee7842 100644
--- a/test/integration/framework/znctest.cpp
+++ b/test/integration/framework/znctest.cpp
@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+#include <QRegularExpression>
 #include "znctest.h"
 
 #ifndef ZNC_BIN_DIR
@@ -119,6 +120,12 @@ std::unique_ptr<QNetworkReply> ZNCTest::HandleHttp(QNetworkReply* reply) {
         std::cout << "Got HTTP reply" << std::endl;
         loop.quit();
     });
+#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
+    QObject::connect(reply, &QNetworkReply::errorOccurred,
+                     [&](QNetworkReply::NetworkError e) {
+                         ADD_FAILURE() << reply->errorString().toStdString();
+                     });
+#else
     QObject::connect(
         reply,
         static_cast<void (QNetworkReply::*)(QNetworkReply::NetworkError)>(
@@ -126,6 +133,7 @@ std::unique_ptr<QNetworkReply> ZNCTest::HandleHttp(QNetworkReply* reply) {
         [&](QNetworkReply::NetworkError e) {
             ADD_FAILURE() << reply->errorString().toStdString();
         });
+#endif
     QTimer::singleShot(30000 /* msec */, &loop, [&]() {
         ADD_FAILURE() << "connection timeout";
         loop.quit();
@@ -160,7 +168,7 @@ void ZNCTest::InstallModule(QString name, QString content) {
         QStringList lines = content.split("\n");
         int maxoffset = -1;
         for (const QString& line : lines) {
-            int nonspace = line.indexOf(QRegExp("\\S"));
+            int nonspace = line.indexOf(QRegularExpression("\\S"));
             if (nonspace == -1) continue;
             if (nonspace < maxoffset || maxoffset == -1) maxoffset = nonspace;
         }