Updated Unix sysinfo backend to treat GTK3 as the only GTK target by:

narrowing the GDK include guard to #if defined(HAVE_GTK3), and

    removing legacy HAVE_GTK2 / HAVE_GTK toolkit label branches from sysinfo_detect_toolkit(),

    narrowing GDK display probing guard in sysinfo_detect_display_backend() to GTK3-only.

Updated Windows and macOS sysinfo backends to remove HAVE_GTK2 / HAVE_GTK fallback labels so sysinfo_detect_toolkit() now returns only "GTK3" (or NULL).

Updated API docs for sysinfo_backend_get_ui() to remove the outdated "GTK2 / X11" example so comments match runtime behavior.

    Removed the deprecated Meson option option('gtk3', ... deprecated: true) from meson_options.txt, leaving gtk-frontend/text-frontend options intact.

    Removed -Dgtk3=true from Debian’s Meson configure flags in debian/rules (override_dh_auto_configure).

    Removed remaining active -Dgtk3=true packaging consumers in Flatpak config:

        dropped it from config-opts

        dropped -Dgtk3=true from cflags.

    Removed -Dgtk3=true from Solus packaging Meson configure args.

    Committed changes on the current branch (e018bfd) and created a PR record via the make_pr tool.

plugins/sysinfo/osx/backend.m

@@ -278,10 +278,6 @@ static const char *sysinfo_detect_toolkit(void)
 {
 #if defined(HAVE_GTK3)
 	return "GTK3";
-#elif defined(HAVE_GTK2)
-	return "GTK2";
-#elif defined(HAVE_GTK)
-	return "GTK";
 #else
 	return NULL;
 #endif

plugins/sysinfo/sysinfo-backend.h

@@ -32,7 +32,7 @@ char *sysinfo_backend_get_network(void);
 
 /*
  * Short description of the UI/toolkit + display backend.
- * Examples: "GTK3 / Wayland", "GTK2 / X11", "Windows / GTK3".
+ * Examples: "GTK3 / Wayland", "Windows / GTK3".
  */
 char *sysinfo_backend_get_ui(void);
 

plugins/sysinfo/unix/backend.c

@@ -19,7 +19,7 @@
 
 #include <glib.h>
 
-#if defined(HAVE_GTK3) || defined(HAVE_GTK2) || defined(HAVE_GTK)
+#if defined(HAVE_GTK3)
 #include <gdk/gdk.h>
 #endif
 #include "parse.h"
@@ -177,10 +177,6 @@ static const char *sysinfo_detect_toolkit(void)
 {
 #if defined(HAVE_GTK3)
 	return "GTK3";
-#elif defined(HAVE_GTK2)
-	return "GTK2";
-#elif defined(HAVE_GTK)
-	return "GTK";
 #else
 	return NULL;
 #endif
@@ -194,7 +190,7 @@ static const char *sysinfo_detect_display_backend(void)
 	const gboolean session_wayland = session && g_ascii_strcasecmp(session, "wayland") == 0;
 
 	/* Best-effort: ask GDK what it actually opened, if available. */
-#if defined(HAVE_GTK3) || defined(HAVE_GTK2) || defined(HAVE_GTK)
+#if defined(HAVE_GTK3)
 	{
 		GdkDisplay *display = gdk_display_get_default();
 		if (display)

plugins/sysinfo/win32/backend.c

@@ -108,10 +108,6 @@ static const char *sysinfo_detect_toolkit(void)
 {
 #if defined(HAVE_GTK3)
 	return "GTK3";
-#elif defined(HAVE_GTK2)
-	return "GTK2";
-#elif defined(HAVE_GTK)
-	return "GTK";
 #else
 	return NULL;
 #endif