I had a similar issue while installing Brawl Star's APK, and after some troubleshooting, I found a method that worked perfectly. First, ensure the APK file is not corrupted by downloading it from a reliable source and checking if it's compatible with your device (32-bit or 64-bit). Next, go to Settings > Apps > Special app access > Install unknown apps and allow installation from your file manager or browser. If your phone still shows "App Not Installed," try freeing up storage space, restarting your phone, and disabling Google Play Protect from the Play Store > Play Protect > Settings to prevent installation blocks. Since you also mentioned the Android/data folder is missing, you might need a third-party file manager like X-plore or ZArchiver to access it, as newer Android versions restrict modifications
Schedule 1 APK in that directory. If all else fails, installing the APK using ADB (Android Debug Bridge) on a PC could bypass system restrictions. Let me know if you need help with that!