diff --git a/CMakeLists.txt b/CMakeLists.txt
index 35c5b0323..df75297e7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -27,7 +27,7 @@
 #   {FEEDLY,GMAIL,INOREADER}_CLIENT_SECRET - preconfigured OAuth cliend SECRET.
 #
 # Other information:
-#   - supports Windows, Linux, macOS, OS/2, Android,
+#   - supports Windows, Linux, *BSD, macOS, OS/2, Android,
 #   - Qt 5.9.0 or newer is required,
 #   - cmake 3.9.0 or newer is required,
 #   - if you wish to make packages for Windows, then you must initialize all submodules within repository before compilation,
@@ -38,13 +38,13 @@
 #   your OS/2 distro is up-to-date and you have all dependencies installed: os2-base, all gcc-* packages,
 #   libc and libcx up-to-date, kbuild-make, ash, binutils, all relevant qt5-* packages.
 #
-#   After your dependecies are installed, then you can compile via standard `qmake -> make -> make install` steps
+#   After your dependecies are installed, then you can compile via standard `cmake -> make -> make install` steps
 #   and package with: 7z.exe a -t7z -mmt -mx9 "rssguard.7z" "<build-folder\src\rssguard\app\*" command.
 #
 # Authors and contributors:
 #   - Martin Rotter (project leader),
 #   - Elbert Pol (OS/2-related contributions),
-#   - CyberTailor (cmake-related contributions.
+#   - Anna Vyalkova (cmake-related contributions).
 #
 #################################################################
 
@@ -98,7 +98,11 @@ if(${FORCE_COLORED_OUTPUT})
   endif()
 endif()
 
+# Aux files not used for build but include in project.
+add_custom_target(AuxFiles SOURCES "resources/scripts/uncrustify/uncrustify.cfg")
+
 # Global compilation switches.
+option(BUILD_WITH_QT6 "Build application with Qt 6" OFF)
 option(USE_WEBENGINE "Use QtWebEngine for embedded web browser" ON)
 option(UPDATE_TRANSLATIONS "Call lupdate to update translation files from source" OFF)
 option(FORCE_COLORED_OUTPUT "Always produce ANSI-colored output (GCC/Clang only)" OFF)
@@ -114,8 +118,7 @@ set(INOREADER_CLIENT_ID "" CACHE STRING "Inoreader client ID")
 set(INOREADER_CLIENT_SECRET "" CACHE STRING "Inoreader client secret")
 
 # Import Qt libraries.
-find_package(QT NAMES Qt6 Qt5 REQUIRED)
-find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS
+set(QT_COMPONENTS
   Core
   Gui
   LinguistTools
@@ -126,26 +129,52 @@ find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS
   Xml
 )
 
-if(QT_VERSION_MAJOR EQUAL 6)
-  find_package(Qt6 COMPONENTS Core5Compat REQUIRED)
+if(NOT OS2)
+  list(APPEND QT_COMPONENTS Multimedia)
 endif()
 
 if(USE_WEBENGINE)
-  find_package(Qt${QT_VERSION_MAJOR} COMPONENTS WebEngineWidgets REQUIRED)
+  list(APPEND QT_COMPONENTS WebEngineWidgets)
   add_compile_definitions(USE_WEBENGINE)
 endif()
 
-if(NOT OS2)
-  find_package(Qt${QT_VERSION_MAJOR} COMPONENTS Multimedia REQUIRED)
-  macro(qt_add_resources)
-    qt_add_big_resources(${ARGN})
-  endmacro()
+if(UNIX AND NOT APPLE AND NOT ANDROID)
+  list(APPEND QT_COMPONENTS DBus)
 endif()
 
-if(UNIX AND NOT APPLE AND NOT ANDROID)
-  find_package(Qt${QT_VERSION_MAJOR} COMPONENTS DBus REQUIRED)
+if(BUILD_WITH_QT6)
+  find_package(QT NAMES Qt6)
+  find_package(Qt6 COMPONENTS ${QT_COMPONENTS} Core5Compat REQUIRED)
+else()
+  find_package(QT NAMES Qt5)
+  find_package(Qt5 COMPONENTS ${QT_COMPONENTS} REQUIRED)
+
+  if(Qt5Core_VERSION VERSION_LESS 5.15.0)
+    # Compatibility macros.
+    macro(qt_add_resources)
+      qt5_add_resources(${ARGN})
+    endmacro()
+
+    macro(qt_add_big_resources)
+      qt5_add_big_resources(${ARGN})
+    endmacro()
+
+    macro(qt_create_translation)
+      qt5_create_translation(${ARGN})
+    endmacro()
+
+    macro(qt_add_translation)
+      qt5_add_translation(${ARGN})
+    endmacro()
+  endif()
 endif()
 
+#if(NOT OS2)
+#  macro(qt_add_resources)
+#    qt_add_big_resources(${ARGN})
+#  endmacro()
+#endif()
+
 # Process oauth service secrets.
 if(NOT FEEDLY_CLIENT_ID STREQUAL "" AND NOT FEEDLY_CLIENT_SECRET STREQUAL "")
   add_compile_definitions(
diff --git a/resources/docs/Documentation.md b/resources/docs/Documentation.md
index 640699a64..fe5a1bc41 100644
--- a/resources/docs/Documentation.md
+++ b/resources/docs/Documentation.md
@@ -45,6 +45,7 @@ I highly recommend to download RSS Guard only from reputable sources.
 RSS Guard is a cross-platform application, and at this point it is known to work on:
 * Windows 7+
 * GNU/Linux (including PinePhone and other Linux-based phone operating systems)
+* BSD (FreeBSD, OpenBSD, NetBSD, etc.)
 * macOS 10.10+
 * OS/2 (ArcaOS, eComStation)
 
diff --git a/src/librssguard/definitions/definitions.h b/src/librssguard/definitions/definitions.h
index cd5fa7445..015358561 100644
--- a/src/librssguard/definitions/definitions.h
+++ b/src/librssguard/definitions/definitions.h
@@ -197,7 +197,7 @@
 #define APP_SKIN_METADATA_FILE "metadata.xml"
 #define APP_STYLE_DEFAULT   "Fusion"
 
-#if defined(Q_OS_LINUX)
+#if defined(Q_OS_UNIX) && !defined(Q_OS_MACOS)
 #define APP_THEME_DEFAULT   ""
 #else
 #define APP_THEME_DEFAULT   "Breeze"
@@ -268,6 +268,12 @@
 
 #if defined(Q_OS_LINUX)
 #define OS_ID   "Linux"
+#elif defined(Q_OS_FREEBSD)
+#define OS_ID   "FreeBSD"
+#elif defined(Q_OS_NETBSD)
+#define OS_ID   "NetBSD"
+#elif defined(Q_OS_OPENBSD)
+#define OS_ID   "OpenBSD"
 #elif defined(Q_OS_OS2)
 #define OS_ID   "OS/2"
 #elif defined(Q_OS_OSX)
@@ -276,6 +282,8 @@
 #define OS_ID   "Windows"
 #elif defined(Q_OS_ANDROID)
 #define OS_ID   "Android"
+#elif defined(Q_OS_UNIX)
+#define OS_ID   "Unix"
 #else
 #define OS_ID   ""
 #endif
@@ -295,7 +303,7 @@
 #define APP_INITIAL_FEEDS_PATH QSL(":/initial_feeds")
 #define APP_LANG_PATH QSL(":/localization")
 
-#if defined(Q_OS_LINUX)
+#if defined(Q_OS_UNIX) && !defined(Q_OS_MACOS)
 #define APP_DESKTOP_SOURCE_ENTRY_FILE "com.github.rssguard.desktop.autostart"
 #define APP_DESKTOP_ENTRY_FILE "com.github.rssguard.desktop"
 
diff --git a/src/librssguard/gui/reusable/helpspoiler.cpp b/src/librssguard/gui/reusable/helpspoiler.cpp
index d1339bc16..b7c3bd9a1 100644
--- a/src/librssguard/gui/reusable/helpspoiler.cpp
+++ b/src/librssguard/gui/reusable/helpspoiler.cpp
@@ -17,7 +17,7 @@
 
 HelpSpoiler::HelpSpoiler(QWidget* parent) : QWidget(parent),
   m_btnToggle(new QToolButton(this)), m_content(new QScrollArea(this)), m_animation(new QParallelAnimationGroup(this)),
-  m_layout(new QGridLayout(this)), m_text(new QLabel(this)) {
+  m_layout(new QGridLayout(this)), m_text(new QLabel(this)), m_btnHelp(new PlainToolButton(this)) {
 
   m_btnToggle->setStyleSheet(QSL("QToolButton { border: none; }"));
   m_btnToggle->setToolButtonStyle(Qt::ToolButtonStyle::ToolButtonTextBesideIcon);
@@ -29,6 +29,7 @@ HelpSpoiler::HelpSpoiler(QWidget* parent) : QWidget(parent),
   m_content->setSizePolicy(QSizePolicy::Policy::Expanding, QSizePolicy::Policy::Fixed);
   m_content->setMaximumHeight(0);
   m_content->setMinimumHeight(0);
+  m_content->setContentsMargins({ 0, 0, 0, 0 });
 
   m_animation->addAnimation(new QPropertyAnimation(this, QSL("minimumHeight").toLocal8Bit()));
   m_animation->addAnimation(new QPropertyAnimation(this, QSL("maximumHeight").toLocal8Bit()));
@@ -39,12 +40,9 @@ HelpSpoiler::HelpSpoiler(QWidget* parent) : QWidget(parent),
   m_layout->setVerticalSpacing(0);
   m_layout->setContentsMargins(0, 0, 0, 0);
 
-  PlainToolButton* btn_help = new PlainToolButton(this);
+  m_btnHelp->setPadding(0);
 
-  btn_help->setPadding(0);
-  btn_help->setIcon(qApp->icons()->fromTheme(QSL("dialog-question")));
-
-  m_layout->addWidget(btn_help, 0, 0);
+  m_layout->addWidget(m_btnHelp, 0, 0);
   m_layout->addWidget(m_btnToggle, 0, 1, 1, 1, Qt::AlignmentFlag::AlignLeft);
   m_layout->addWidget(m_content, 1, 0, 1, 2);
 
@@ -79,6 +77,7 @@ HelpSpoiler::HelpSpoiler(QWidget* parent) : QWidget(parent),
     m_animation->start();
   });
 
+  m_text->setMargin(0);
   m_text->setWordWrap(true);
 
   auto* content_layout = new QVBoxLayout(m_content);
@@ -93,5 +92,7 @@ void HelpSpoiler::setHelpText(const QString& title, const QString& text, bool is
 
 void HelpSpoiler::setHelpText(const QString& text, bool is_warning) {
   m_text->setText(text);
-  GuiUtilities::setLabelAsNotice(*m_text, is_warning, false);
+  m_btnHelp->setIcon(is_warning
+                       ? qApp->icons()->fromTheme(QSL("dialog-warning"))
+                       : qApp->icons()->fromTheme(QSL("dialog-question")));
 }
diff --git a/src/librssguard/gui/reusable/helpspoiler.h b/src/librssguard/gui/reusable/helpspoiler.h
index 5790ae43b..9014ed6fb 100644
--- a/src/librssguard/gui/reusable/helpspoiler.h
+++ b/src/librssguard/gui/reusable/helpspoiler.h
@@ -10,6 +10,7 @@ class QGridLayout;
 class QToolButton;
 class QParallelAnimationGroup;
 class QScrollArea;
+class PlainToolButton;
 
 class HelpSpoiler : public QWidget {
   Q_OBJECT
@@ -26,6 +27,7 @@ class HelpSpoiler : public QWidget {
     QParallelAnimationGroup* m_animation;
     QGridLayout* m_layout;
     QLabel* m_text;
+    PlainToolButton* m_btnHelp;
 };
 
 #endif // HELPSPOILER_H
diff --git a/src/librssguard/gui/settings/settingsbrowsermail.cpp b/src/librssguard/gui/settings/settingsbrowsermail.cpp
index 5572bbb64..f3ccd9d65 100644
--- a/src/librssguard/gui/settings/settingsbrowsermail.cpp
+++ b/src/librssguard/gui/settings/settingsbrowsermail.cpp
@@ -82,7 +82,7 @@ void SettingsBrowserMail::selectBrowserExecutable() {
                                                                qApp->homeFolder(),
 
                                                                //: File filter for external browser selection dialog.
-#if defined(Q_OS_LINUX)
+#if defined(Q_OS_UNIX) && !defined(Q_OS_MACOS)
                                                                tr("Executables (*)"));
 #else
                                                                tr("Executables (*.*)"));
@@ -126,7 +126,7 @@ void SettingsBrowserMail::selectEmailExecutable() {
                                                          qApp->homeFolder(),
 
                                                          //: File filter for external e-mail selection dialog.
-#if defined(Q_OS_LINUX)
+#if defined(Q_OS_UNIX) && !defined(Q_OS_MACOS)
                                                          tr("Executables (*)"));
 #else
                                                          tr("Executables (*.*)"));
diff --git a/src/librssguard/gui/settings/settingsgui.cpp b/src/librssguard/gui/settings/settingsgui.cpp
index cab1230a2..7a9963a29 100644
--- a/src/librssguard/gui/settings/settingsgui.cpp
+++ b/src/librssguard/gui/settings/settingsgui.cpp
@@ -132,7 +132,7 @@ void SettingsGui::loadSettings() {
     if (icon_theme_name == QSL(APP_NO_THEME)) {
       // Add just "no theme" on other systems.
       //: Label for disabling icon theme.
-#if defined(Q_OS_LINUX)
+#if defined(Q_OS_UNIX) && !defined(Q_OS_MACOS)
       m_ui->m_cmbIconTheme->addItem(tr("system icon theme"), APP_NO_THEME);
 #else
       m_ui->m_cmbIconTheme->addItem(tr("no icon theme"), APP_NO_THEME);
diff --git a/src/librssguard/miscellaneous/application.cpp b/src/librssguard/miscellaneous/application.cpp
index b4a10a292..4b67cabd5 100644
--- a/src/librssguard/miscellaneous/application.cpp
+++ b/src/librssguard/miscellaneous/application.cpp
@@ -31,7 +31,7 @@
 #include <QSslSocket>
 #include <QTimer>
 
-#if defined(Q_OS_LINUX)
+#if defined(Q_OS_UNIX) && !defined(Q_OS_MACOS)
 #include <QDBusConnection>
 #include <QDBusMessage>
 #endif
@@ -91,7 +91,7 @@ Application::Application(const QString& id, int& argc, char** argv)
   connect(this, &Application::commitDataRequest, this, &Application::onCommitData);
   connect(this, &Application::saveStateRequest, this, &Application::onSaveState);
 
-#if defined(Q_OS_LINUX)
+#if defined(Q_OS_UNIX) && !defined(Q_OS_MACOS)
   QString app_dir = QString::fromLocal8Bit(qgetenv("APPDIR"));
 
   if (!app_dir.isEmpty()) {
@@ -623,7 +623,7 @@ void Application::showMessagesNumber(int unread_messages, bool any_feed_has_unre
     m_trayIcon->setNumber(unread_messages, any_feed_has_unread_messages);
   }
 
-#if defined(Q_OS_LINUX)
+#if defined(Q_OS_UNIX) && !defined(Q_OS_MACOS)
   QDBusMessage signal = QDBusMessage::createSignal(QSL("/"),
                                                    QSL("com.canonical.Unity.LauncherEntry"),
                                                    QSL("Update"));
diff --git a/src/librssguard/miscellaneous/iconfactory.cpp b/src/librssguard/miscellaneous/iconfactory.cpp
index 8b0190437..5cbda1d49 100644
--- a/src/librssguard/miscellaneous/iconfactory.cpp
+++ b/src/librssguard/miscellaneous/iconfactory.cpp
@@ -92,7 +92,7 @@ void IconFactory::loadCurrentIconTheme() {
 
   if (installed_themes.contains(theme_name_from_settings)) {
     // Desired icon theme is installed and can be loaded.
-#if defined(Q_OS_LINUX)
+#if defined(Q_OS_UNIX) && !defined(Q_OS_MACOS)
     if (theme_name_from_settings.isEmpty()) {
       qDebugNN << LOGSEC_GUI << "Loading default system icon theme.";
     }
@@ -108,7 +108,7 @@ void IconFactory::loadCurrentIconTheme() {
   else {
     // Desired icon theme is not currently available.
     // Activate "default" or "no" icon theme instead.
-#if defined(Q_OS_LINUX)
+#if defined(Q_OS_UNIX) && !defined(Q_OS_MACOS)
     qWarningNN << "Icon theme"
                << QUOTE_W_SPACE(theme_name_from_settings)
                << "cannot be loaded because it is not installed. Activating \"no\" icon theme.";
diff --git a/src/librssguard/miscellaneous/settings.cpp b/src/librssguard/miscellaneous/settings.cpp
index b1e5935e8..787947879 100644
--- a/src/librssguard/miscellaneous/settings.cpp
+++ b/src/librssguard/miscellaneous/settings.cpp
@@ -491,8 +491,8 @@ SettingsProperties Settings::determineProperties() {
   else {
     // We will use PORTABLE settings only and only if it is available and NON-PORTABLE
     // settings was not initialized before.
-#if defined(Q_OS_LINUX) || defined (Q_OS_ANDROID) || defined (Q_OS_MACOSOS)
-    // DO NOT use portable settings for Linux, it is really not used on that platform.
+#if defined(Q_OS_UNIX)
+    // DO NOT use portable settings for *nix, it is really not used on that platform.
     const bool will_we_use_portable_settings = false;
 #else
     const QString exe_path = qApp->applicationDirPath();
diff --git a/src/librssguard/miscellaneous/systemfactory.cpp b/src/librssguard/miscellaneous/systemfactory.cpp
index 6f4598a77..db2321b5d 100644
--- a/src/librssguard/miscellaneous/systemfactory.cpp
+++ b/src/librssguard/miscellaneous/systemfactory.cpp
@@ -58,8 +58,8 @@ SystemFactory::AutoStartStatus SystemFactory::autoStartStatus() const {
   else {
     return AutoStartStatus::Disabled;
   }
-#elif defined(Q_OS_LINUX)
-  // Use proper freedesktop.org way to auto-start the application on Linux.
+#elif defined(Q_OS_UNIX) && !defined(Q_OS_MACOS)
+  // Use proper freedesktop.org way to auto-start the application.
   // INFO: http://standards.freedesktop.org/autostart-spec/latest/
   const QString desktop_file_location = autostartDesktopFileLocation();
 
@@ -86,7 +86,7 @@ SystemFactory::AutoStartStatus SystemFactory::autoStartStatus() const {
 #endif
 }
 
-#if defined(Q_OS_LINUX)
+#if defined(Q_OS_UNIX) && !defined(Q_OS_MACOS)
 QString SystemFactory::autostartDesktopFileLocation() const {
   const QString xdg_config_path(qgetenv("XDG_CONFIG_HOME"));
   QString desktop_file_location;
@@ -136,7 +136,7 @@ bool SystemFactory::setAutoStartStatus(AutoStartStatus new_status) {
     default:
       return false;
   }
-#elif defined(Q_OS_LINUX)
+#elif defined(Q_OS_UNIX) && !defined(Q_OS_MACOS)
   // Note that we expect here that no other program uses
   // "rssguard.desktop" desktop file.
   const QString destination_file = autostartDesktopFileLocation();
diff --git a/src/librssguard/miscellaneous/systemfactory.h b/src/librssguard/miscellaneous/systemfactory.h
index e32b4af6c..3048e6705 100644
--- a/src/librssguard/miscellaneous/systemfactory.h
+++ b/src/librssguard/miscellaneous/systemfactory.h
@@ -55,7 +55,7 @@ class SystemFactory : public QObject {
     // new status failed.
     bool setAutoStartStatus(AutoStartStatus new_status);
 
-#if defined(Q_OS_LINUX)
+#if defined(Q_OS_UNIX) && !defined(Q_OS_MACOS)
     // Returns standard location where auto-start .desktop files
     // should be placed.
     QString autostartDesktopFileLocation() const;
diff --git a/src/librssguard/network-web/webfactory.cpp b/src/librssguard/network-web/webfactory.cpp
index ee08d7f59..c26dbabea 100644
--- a/src/librssguard/network-web/webfactory.cpp
+++ b/src/librssguard/network-web/webfactory.cpp
@@ -306,7 +306,7 @@ void WebFactory::createMenu(QMenu* menu) {
   actions << createEngineSettingsAction(tr("Plugins enabled"), QWebEngineSettings::WebAttribute::PluginsEnabled);
   actions << createEngineSettingsAction(tr("Fullscreen enabled"), QWebEngineSettings::WebAttribute::FullScreenSupportEnabled);
 
-#if !defined(Q_OS_LINUX)
+#if !defined(Q_OS_UNIX) && !defined(Q_OS_MACOS)
   actions << createEngineSettingsAction(tr("Screen capture enabled"), QWebEngineSettings::WebAttribute::ScreenCaptureEnabled);
   actions << createEngineSettingsAction(tr("WebGL enabled"), QWebEngineSettings::WebAttribute::WebGLEnabled);
   actions << createEngineSettingsAction(tr("Accelerate 2D canvas"), QWebEngineSettings::WebAttribute::Accelerated2dCanvasEnabled);
diff --git a/src/librssguard/services/standard/gui/standardfeeddetails.ui b/src/librssguard/services/standard/gui/standardfeeddetails.ui
index e01acfc1b..bb815e0b6 100644
--- a/src/librssguard/services/standard/gui/standardfeeddetails.ui
+++ b/src/librssguard/services/standard/gui/standardfeeddetails.ui
@@ -112,7 +112,7 @@
      <property name="minimumSize">
       <size>
        <width>0</width>
-       <height>70</height>
+       <height>50</height>
       </size>
      </property>
      <property name="maximumSize">
@@ -138,7 +138,7 @@
      <property name="minimumSize">
       <size>
        <width>0</width>
-       <height>70</height>
+       <height>50</height>
       </size>
      </property>
      <property name="maximumSize">
diff --git a/src/rssguard/main.cpp b/src/rssguard/main.cpp
index 740b58fdc..55cff7c7e 100644
--- a/src/rssguard/main.cpp
+++ b/src/rssguard/main.cpp
@@ -33,7 +33,7 @@ int main(int argc, char* argv[]) {
   QApplication::setAttribute(Qt::ApplicationAttribute::AA_EnableHighDpiScaling);
 #endif
 
-#if defined(Q_OS_LINUX)
+#if defined(Q_OS_UNIX) && !defined(Q_OS_MACOS)
   QApplication::setDesktopFileName(APP_DESKTOP_ENTRY_FILE);
 #endif