pantheon.elementary-session-settings: Drop x11 session

The fallback-session option is not used in wayland session, and also
ignored in gnome-session 49.

nixos/doc/manual/release-notes/rl-2511.section.md

@@ -252,7 +252,7 @@
 
 - mate-wayland-session 1.28.4 is now using the default wayfire decorator instead of firedecor, thus `services.xserver.desktopManager.mate.enableWaylandSession` is no longer shipping firedecor. If you are experiencing broken window decorations after upgrade, backup and remove `~/.config/mate/wayfire.ini` and re-login.
 
-- Due to [deprecation of gnome-session X11 support](https://blogs.gnome.org/alatiera/2025/06/08/the-x11-session-removal/), `services.desktopManager.pantheon` now defaults to pantheon-wayland session. The X11 session will be removed before gnome-session 49 lands.
+- Due to [deprecation of gnome-session X11 support](https://blogs.gnome.org/alatiera/2025/06/08/the-x11-session-removal/), `services.desktopManager.pantheon` now defaults to pantheon-wayland session. The X11 session has been removed, see [this issue](https://github.com/elementary/session-settings/issues/91) for details.
 
 - `services.gitea` supports sending notifications with sendmail again. To do this, activate the parameter `services.gitea.mailerUseSendmail` and configure SMTP server.
 

pkgs/desktops/pantheon/desktop/elementary-session-settings/default.nix

@@ -58,8 +58,9 @@ stdenv.mkDerivation rec {
 
   mesonFlags = [
     "-Dmimeapps-list=false"
-    "-Dfallback-session=GNOME"
     "-Ddetect-program-prefixes=true"
+    # https://github.com/elementary/session-settings/issues/91
+    "-Dx11=false"
     "--sysconfdir=${placeholder "out"}/etc"
   ];
 
@@ -70,7 +71,7 @@ stdenv.mkDerivation rec {
     cp -av ${./pantheon-mimeapps.list} $out/share/applications/pantheon-mimeapps.list
 
     # absolute path patched sessions
-    substituteInPlace $out/share/{xsessions/pantheon.desktop,wayland-sessions/pantheon-wayland.desktop} \
+    substituteInPlace $out/share/wayland-sessions/pantheon-wayland.desktop \
       --replace-fail "Exec=gnome-session" "Exec=${gnome-session}/bin/gnome-session" \
       --replace-fail "TryExec=io.elementary.wingpanel" "TryExec=${wingpanel}/bin/io.elementary.wingpanel"
   '';
@@ -79,7 +80,6 @@ stdenv.mkDerivation rec {
     updateScript = nix-update-script { };
 
     providedSessions = [
-      "pantheon"
       "pantheon-wayland"
     ];
   };