Set fallback chain for page slug calculation

public/typo3conf/ext/ep_theme/Configuration/TCA/Overrides/pages.php

@@ -116,5 +116,12 @@ call_user_func(function() {
         'EP Theme'
     );
 
+    $GLOBALS['TCA']['pages']['columns']['slug']['config']['generatorOptions']['fields'] = [
+        [
+            'nav_title',
+            'title'
+        ]
+    ];
+
 });