Cherry-pick patch to fix installer crash when using lomiri-greeter

LP: #2143868

debian/patches/lightdm-greeter-path.patch

@@ -0,0 +1,44 @@
+From: Adriaan de Groot <groot@kde.org>
+Date: Tue, 10 Mar 2026 14:49:55 +0100
+Subject: [displaymanager] Support alternative greeter paths in lightdm
+
+Origin: upstream 3.4.2
+---
+ src/modules/displaymanager/main.py | 24 ++++++++++++++----------
+ 1 file changed, 14 insertions(+), 10 deletions(-)
+
+diff --git a/src/modules/displaymanager/main.py b/src/modules/displaymanager/main.py
+index 73a884df7..143b0db15 100644
+--- a/src/modules/displaymanager/main.py
++++ b/src/modules/displaymanager/main.py
+@@ -664,16 +664,20 @@ class DMlightdm(DisplayManager):
+         a .desktop file that specifies where the actual executable is. May return
+         None to indicate nothing-was-found.
+         """
+-        greeters_dir = "usr/share/xgreeters"
+-        greeters_target_path = os.path.join(self.root_mount_point, greeters_dir)
+-        available_names = os.listdir(greeters_target_path)
+-        available_names.sort()
+-        desktop_names = [n for n in self.preferred_greeters if n in available_names] # Preferred ones
+-        if desktop_names:
+-            return desktop_names[0]
+-        desktop_names = [n for n in available_names if n.endswith(".desktop")] # .. otherwise any .desktop
+-        if desktop_names:
+-            return desktop_names[0]
++        for greeters_dir in ( "usr/share/xgreeters", "usr/share/lightdm/greeters", ):
++            greeters_target_path = os.path.join(self.root_mount_point, greeters_dir)
++            available_names = []
++            try:
++                available_names = os.listdir(greeters_target_path)
++            except FileNotFoundError:
++                continue
++            available_names.sort()
++            desktop_names = [n for n in self.preferred_greeters if n in available_names] # Preferred ones
++            if desktop_names:
++                return desktop_names[0]
++            desktop_names = [n for n in available_names if n.endswith(".desktop")] # .. otherwise any .desktop
++            if desktop_names:
++                return desktop_names[0]
+         return None
+ 
+     def greeter_setup(self):

debian/patches/series

@@ -8,3 +8,4 @@ repair-icon-size.patch
 populate-bootloader-installation-path.patch
 allow-ignore-software-db-update-failure.patch
 sddm-test-fix.patch
+lightdm-greeter-patch.patch