Update SteamOS GPU flags for improved compatibility

Refined GPU command line switches for SteamOS/Gamescope in main.js to use ANGLE with X11, enable VulkanFromANGLE, and adjust feature flags. Updated the start:steamos script in package.json to match these changes for better webview rendering and stability on Steam Deck.

main.js

@@ -61,19 +61,18 @@ if (process.platform === 'linux') {
     console.log(`[GPU] SteamOS/Gamescope DETECTED: ${detectionReason}`);
     console.log('[GPU] Applying SteamOS-specific GPU flags for webview rendering...');
     
-    // Critical flags for SteamOS/Gamescope webview rendering
-    // SteamOS only supports egl-angle, NOT desktop GL
+    // SteamOS GPU flags - use ANGLE for rendering
     app.commandLine.appendSwitch('ozone-platform', 'x11');
-    app.commandLine.appendSwitch('use-gl', 'egl');
-    app.commandLine.appendSwitch('use-angle', 'default');
-    app.commandLine.appendSwitch('disable-gpu-compositing');
-    app.commandLine.appendSwitch('disable-gpu-vsync');
-    app.commandLine.appendSwitch('disable-software-rasterizer');
-    app.commandLine.appendSwitch('disable-features', 'VizDisplayCompositor,UseChromeOSDirectVideoDecoder');
-    app.commandLine.appendSwitch('enable-features', 'UseOzonePlatform,Vulkan');
+    app.commandLine.appendSwitch('use-angle', 'gl');
+    app.commandLine.appendSwitch('angle-platform-type', 'x11');
     
-    // In-process GPU can help with stability on Steam Deck
+    // GPU process settings
     app.commandLine.appendSwitch('in-process-gpu');
+    app.commandLine.appendSwitch('disable-gpu-vsync');
+    
+    // Feature flags
+    app.commandLine.appendSwitch('enable-features', 'VulkanFromANGLE,UseOzonePlatform');
+    app.commandLine.appendSwitch('disable-features', 'VizDisplayCompositor');
   } else {
     console.log('[GPU] Standard Linux environment detected');