diff --git a/StarterNG/Classes/Settings.cs b/StarterNG/Classes/Settings.cs
index 477399b..f5a6528 100644
--- a/StarterNG/Classes/Settings.cs
+++ b/StarterNG/Classes/Settings.cs
@@ -9,6 +9,8 @@ namespace StarterNG.Classes;
 
 public enum BatteryDefault { Default = 0, AlwaysOff = 1, AlwaysOn = 2 }
 
+public enum ExeProblem { None, NotFound, NotExecutable, WrongPlatform }
+
 public sealed class Settings
 {
     public static Settings Instance { get; } = new();
@@ -114,7 +116,6 @@ public sealed class Settings
     public bool DrivableOnly = true;
     public bool ShowArchivalSceneries = true;
     public bool HideArchivalVehicles = true;
-
     public string LastScenery = "";
 
     public static readonly string[] RenderEngines =
@@ -159,33 +160,87 @@ public sealed class Settings
     public static string UserConfigDirectory() =>
         Path.GetDirectoryName(UserConfigPath()) ?? AppContext.BaseDirectory;
 
-    public string ResolveExecutable()
+    public string ResolveExecutable() => ResolveExecutable(out _);
+
+    public string ResolveExecutable(out ExeProblem problem)
     {
         if (!SelectExeAutomatically && !string.IsNullOrWhiteSpace(ExecutablePath))
+        {
+            problem = ValidateExecutable(FullPath(ExecutablePath));
             return ExecutablePath;
+        }
 
         string canonical = OperatingSystem.IsWindows() ? "eu07.exe" : "eu07";
+        string? fallback = null;
         try
         {
-            string? best = null;
-            foreach (string path in Directory.GetFiles(Directory.GetCurrentDirectory(), "eu07*"))
+            var candidates = Directory.GetFiles(Directory.GetCurrentDirectory(), "eu07*")
+                .Where(IsExecutableCandidate)
+                .OrderBy(p => string.Equals(Path.GetFileName(p), canonical, StringComparison.OrdinalIgnoreCase) ? 0 : 1)
+                .ThenBy(p => Path.GetFileName(p)!.Length);
+
+            foreach (string path in candidates)
             {
-                if (!IsExecutableCandidate(path))
-                    continue;
-                string file = Path.GetFileName(path);
-                if (string.Equals(file, canonical, StringComparison.OrdinalIgnoreCase))
+                if (ValidateExecutable(path) == ExeProblem.None)
+                {
+                    problem = ExeProblem.None;
                     return path;
-                if (best == null || file.Length < Path.GetFileName(best).Length)
-                    best = path;
+                }
+                fallback ??= path;
             }
-            if (best != null)
-                return best;
         }
         catch {  }
 
+        if (fallback != null)
+        {
+            problem = ValidateExecutable(fallback);
+            return fallback;
+        }
+
+        problem = ExeProblem.NotFound;
         return canonical;
     }
 
+    private static string FullPath(string path) =>
+        Path.IsPathRooted(path) ? path : Path.Combine(Directory.GetCurrentDirectory(), path);
+
+    public static ExeProblem ValidateExecutable(string path)
+    {
+        try
+        {
+            if (!File.Exists(path))
+                return ExeProblem.NotFound;
+
+            if (!OperatingSystem.IsWindows())
+            {
+                const UnixFileMode anyExecute =
+                    UnixFileMode.UserExecute | UnixFileMode.GroupExecute | UnixFileMode.OtherExecute;
+                if ((File.GetUnixFileMode(path) & anyExecute) == 0)
+                    return ExeProblem.NotExecutable;
+            }
+
+            byte[] head = new byte[4];
+            using (var fs = File.OpenRead(path))
+            {
+                if (fs.Read(head, 0, 4) == 4)
+                {
+                    bool pe = head[0] == 0x4D && head[1] == 0x5A;
+                    bool elf = head[0] == 0x7F && head[1] == 0x45 && head[2] == 0x4C && head[3] == 0x46;
+                    if (OperatingSystem.IsWindows() && elf)
+                        return ExeProblem.WrongPlatform;
+                    if (OperatingSystem.IsLinux() && pe)
+                        return ExeProblem.WrongPlatform;
+                }
+            }
+
+            return ExeProblem.None;
+        }
+        catch
+        {
+            return ExeProblem.NotFound;
+        }
+    }
+
     public static List<string> ListCandidateExecutables(string? directory = null)
     {
         directory ??= Directory.GetCurrentDirectory();
@@ -208,6 +263,8 @@ public sealed class Settings
             return false;
         if (OperatingSystem.IsWindows())
             return ext == ".exe";
+        if (OperatingSystem.IsLinux())
+            return ext.Length == 0 || ext is ".x86_64" or ".run" or ".appimage";
 
         return ext.Length == 0 || ext is ".exe" or ".x86_64" or ".run" or ".appimage";
     }
@@ -270,7 +327,6 @@ public sealed class Settings
     {
         WriteToConfig();
         ApplyFramebufferFidelity();
-        ApplyHdrShader();
 
         try
         {
@@ -331,39 +387,6 @@ public sealed class Settings
             _config.Remove("gfx.framebuffer.fidelity");
     }
 
-    public void ApplyHdrShader()
-    {
-
-        if (RenderEngine is not (0 or 1 or 5))
-            return;
-
-        string? src = FindBundled("Reinhard.glsl");
-        if (src is null) return;
-
-        try
-        {
-            string destDir = Path.Combine(Directory.GetCurrentDirectory(), "shaders");
-            Directory.CreateDirectory(destDir);
-            File.Copy(src, Path.Combine(destDir, "tonemapping.glsl"), overwrite: true);
-        }
-        catch {  }
-    }
-
-    private static string? FindBundled(string fileName)
-    {
-        foreach (string dir in new[]
-                 {
-                     Path.Combine(Directory.GetCurrentDirectory(), "starter"),
-                     Path.Combine(AppContext.BaseDirectory, "startercfg"),
-                     Path.Combine(Directory.GetCurrentDirectory(), "startercfg")
-                 })
-        {
-            string path = Path.Combine(dir, fileName);
-            if (File.Exists(path)) return path;
-        }
-        return null;
-    }
-
     public void DumpMissingVehicleLog()
     {
         if (!LogMissingVehicleFiles) return;
@@ -506,10 +529,18 @@ public sealed class Settings
         LastScenery = c.GetString("starter.last.scenery", "");
     }
 
+    private static readonly string[] ObsoleteKeys =
+    {
+        "gfx.postfx.tonemapping",
+    };
+
     private void WriteToConfig()
     {
         var c = _config;
 
+        foreach (string key in ObsoleteKeys)
+            c.Remove(key);
+
         c.Set("lang", Language == "Polski" ? "pl" : "en");
         c.SetBool("fullscreen", Fullscreen);
         c.SetBool("inactivepause", PauseWhenInactive);
diff --git a/StarterNG/MainWindow.axaml.cs b/StarterNG/MainWindow.axaml.cs
index 0ea06b4..8907906 100644
--- a/StarterNG/MainWindow.axaml.cs
+++ b/StarterNG/MainWindow.axaml.cs
@@ -4,6 +4,7 @@ using System.IO;
 using System.Linq;
 using System.Text;
 using System.Threading;
+using System.Threading.Tasks;
 using Avalonia;
 using Avalonia.Controls;
 using Avalonia.Input;
@@ -223,6 +224,18 @@ public partial class MainWindow : Window
         return trainset.Vehicles.Any(CanStart);
     }
 
+    private Task<bool> ShowExeProblem(ExeProblem problem, string exe)
+    {
+        string key = problem switch
+        {
+            ExeProblem.NotExecutable => "ExeNotExecutable",
+            ExeProblem.WrongPlatform => "ExeWrongPlatform",
+            _ => "ExeNotFound"
+        };
+        return MessageBox.Show(this, $"{exe}\n\n{App.Loc[key]}",
+            App.Loc["ExeLaunchFailed"], MessageBoxButtons.Ok);
+    }
+
     private async void StartButton_OnClick(object? sender, RoutedEventArgs e)
     {
         var scenery = AppState.Instance.CurrentScenery;
@@ -271,10 +284,16 @@ public partial class MainWindow : Window
 
         SettingsModel.Instance.CaptureAndSave();
 
+        string exe = Path.GetFullPath(SettingsModel.Instance.ResolveExecutable(out var exeProblem));
+        if (exeProblem != ExeProblem.None)
+        {
+            await ShowExeProblem(exeProblem, exe);
+            return;
+        }
+
         Process? sim;
         try
         {
-            string exe = Path.GetFullPath(SettingsModel.Instance.ResolveExecutable());
             sim = Process.Start(new ProcessStartInfo
             {
                 FileName = exe,
@@ -283,8 +302,10 @@ public partial class MainWindow : Window
                 UseShellExecute = false
             });
         }
-        catch
+        catch (Exception ex)
         {
+            await MessageBox.Show(this, $"{exe}\n\n{ex.Message}",
+                App.Loc["ExeLaunchFailed"], MessageBoxButtons.Ok);
             return;
         }
 
diff --git a/StarterNG/Views/MessageBox.cs b/StarterNG/Views/MessageBox.cs
index 035a674..ef12289 100644
--- a/StarterNG/Views/MessageBox.cs
+++ b/StarterNG/Views/MessageBox.cs
@@ -7,13 +7,13 @@ namespace StarterNG.Views;
 
 public enum MessageBoxButtons
 {
-    YesNo
+    YesNo,
+    Ok
 }
 
 public static class MessageBox
 {
-
-    public static async Task<bool> Show(Window owner, string message, string title, MessageBoxButtons _)
+    public static async Task<bool> Show(Window owner, string message, string title, MessageBoxButtons buttons)
     {
         var win = new Window
         {
@@ -33,6 +33,12 @@ public static class MessageBox
         noBtn.Classes.Add("Flat");
         noBtn.Click += (_, _) => win.Close();
 
+        if (buttons == MessageBoxButtons.Ok)
+        {
+            yesBtn.Content = App.Loc["Ok"];
+            noBtn.IsVisible = false;
+        }
+
         win.Content = new StackPanel
         {
             Margin = new Avalonia.Thickness(16),
diff --git a/StarterNG/Views/Settings.axaml.cs b/StarterNG/Views/Settings.axaml.cs
index 4365f8d..675a524 100644
--- a/StarterNG/Views/Settings.axaml.cs
+++ b/StarterNG/Views/Settings.axaml.cs
@@ -158,9 +158,20 @@ public partial class Settings : UserControl
             UartRadioChannelCb.IsChecked = s.UartRadioChannel;
             UpdateFeedbackDetailVisibility();
 
-            SelectExeCb.SelectedIndex = s.SelectExeAutomatically
-                ? 0
-                : Math.Max(0, FindComboIndexByContent(SelectExeCb, s.ExecutablePath));
+            if (s.SelectExeAutomatically)
+            {
+                SelectExeCb.SelectedIndex = 0;
+            }
+            else
+            {
+                int exeIdx = FindComboIndexByContent(SelectExeCb, s.ExecutablePath);
+                if (exeIdx < 0)
+                {
+                    SelectExeCb.Items.Add(new ComboBoxItem { Content = s.ExecutablePath });
+                    exeIdx = SelectExeCb.Items.Count - 1;
+                }
+                SelectExeCb.SelectedIndex = exeIdx;
+            }
             DebugModeCb.IsChecked = s.DebugMode;
             VirtualShuntingCb.IsChecked = s.VirtualShunting;
             LogMissingVehicleFilesCb.IsChecked = s.LogMissingVehicleFiles;
diff --git a/StarterNG/startercfg/lang/cz.xml b/StarterNG/startercfg/lang/cz.xml
index 8cc2e7a..df5a136 100644
--- a/StarterNG/startercfg/lang/cz.xml
+++ b/StarterNG/startercfg/lang/cz.xml
@@ -222,6 +222,11 @@
     <String key="Cancel">Zrušit</String>
     <String key="Yes">Ano</String>
     <String key="No">Ne</String>
+    <String key="Ok">OK</String>
+    <String key="ExeLaunchFailed">Nepodařilo se spustit simulátor</String>
+    <String key="ExeNotFound">Spustitelný soubor simulátoru nebyl nalezen.</String>
+    <String key="ExeNotExecutable">Soubor není označen jako spustitelný (chmod +x).</String>
+    <String key="ExeWrongPlatform">Tento binární soubor je pro jiný operační systém.</String>
     <String key="TabInfo">Informace</String>
     <String key="SettingsFileChangedTitle">Nastavení</String>
     <String key="SettingsFileChanged">Soubor eu07.ini byl změněn mimo starter. Načíst jej znovu?</String>
diff --git a/StarterNG/startercfg/lang/en.xml b/StarterNG/startercfg/lang/en.xml
index fc8ec32..59beaff 100644
--- a/StarterNG/startercfg/lang/en.xml
+++ b/StarterNG/startercfg/lang/en.xml
@@ -222,6 +222,11 @@
     <String key="Cancel">Cancel</String>
     <String key="Yes">Yes</String>
     <String key="No">No</String>
+    <String key="Ok">OK</String>
+    <String key="ExeLaunchFailed">Could not start the simulator</String>
+    <String key="ExeNotFound">The simulator executable was not found.</String>
+    <String key="ExeNotExecutable">The file is not marked as executable (chmod +x).</String>
+    <String key="ExeWrongPlatform">This binary is built for a different operating system.</String>
     <String key="TabInfo">Info</String>
     <String key="SettingsFileChangedTitle">Settings</String>
     <String key="SettingsFileChanged">eu07.ini was changed outside the starter. Reload it?</String>
diff --git a/StarterNG/startercfg/lang/hu.xml b/StarterNG/startercfg/lang/hu.xml
index 0ff8c56..d3dfd6a 100644
--- a/StarterNG/startercfg/lang/hu.xml
+++ b/StarterNG/startercfg/lang/hu.xml
@@ -222,6 +222,11 @@
     <String key="Cancel">Mégse</String>
     <String key="Yes">Igen</String>
     <String key="No">Nem</String>
+    <String key="Ok">OK</String>
+    <String key="ExeLaunchFailed">A szimulátor indítása sikertelen</String>
+    <String key="ExeNotFound">A szimulátor futtatható fájlja nem található.</String>
+    <String key="ExeNotExecutable">A fájl nincs futtathatóként megjelölve (chmod +x).</String>
+    <String key="ExeWrongPlatform">Ez a bináris másik operációs rendszerhez készült.</String>
     <String key="TabInfo">Információ</String>
     <String key="SettingsFileChangedTitle">Beállítások</String>
     <String key="SettingsFileChanged">Az eu07.ini fájl a starteren kívül módosult. Újratölti?</String>
diff --git a/StarterNG/startercfg/lang/pl.xml b/StarterNG/startercfg/lang/pl.xml
index 3bc69cc..3699fea 100644
--- a/StarterNG/startercfg/lang/pl.xml
+++ b/StarterNG/startercfg/lang/pl.xml
@@ -222,6 +222,11 @@
     <String key="Cancel">Anuluj</String>
     <String key="Yes">Tak</String>
     <String key="No">Nie</String>
+    <String key="Ok">OK</String>
+    <String key="ExeLaunchFailed">Nie udało się uruchomić symulatora</String>
+    <String key="ExeNotFound">Nie znaleziono pliku wykonywalnego symulatora.</String>
+    <String key="ExeNotExecutable">Plik nie ma prawa wykonywania (chmod +x).</String>
+    <String key="ExeWrongPlatform">To jest plik wykonywalny dla innego systemu niż uruchomiony.</String>
     <String key="TabInfo">Informacje</String>
     <String key="SettingsFileChangedTitle">Ustawienia</String>
     <String key="SettingsFileChanged">Plik eu07.ini został zmieniony poza starterem. Wczytać ponownie?</String>
diff --git a/StarterNG/startercfg/lang/ru.xml b/StarterNG/startercfg/lang/ru.xml
index 8fff66c..1cc4f2b 100644
--- a/StarterNG/startercfg/lang/ru.xml
+++ b/StarterNG/startercfg/lang/ru.xml
@@ -222,6 +222,11 @@
     <String key="Cancel">Отмена</String>
     <String key="Yes">Да</String>
     <String key="No">Нет</String>
+    <String key="Ok">OK</String>
+    <String key="ExeLaunchFailed">Не удалось запустить симулятор</String>
+    <String key="ExeNotFound">Исполняемый файл симулятора не найден.</String>
+    <String key="ExeNotExecutable">Файл не помечен как исполняемый (chmod +x).</String>
+    <String key="ExeWrongPlatform">Этот исполняемый файл собран для другой операционной системы.</String>
     <String key="TabInfo">Информация</String>
     <String key="SettingsFileChangedTitle">Настройки</String>
     <String key="SettingsFileChanged">Файл eu07.ini изменён вне стартера. Загрузить заново?</String>