Complete One UI - Substratum System Mods is a personalization app developed by Osuki Fujioka available for Android devices. The app is designed to fix the annoying UI bugs that Samsung has not yet resolved and to complete the Night Mode UI. The app also tweaks the UI for better user experience.

This app is compatible with Android 10 (Q), and it is Substratum-based. To use the app, you need to download Synergy and Substratum Lite. For S9/S9+ and N9 on Android 9, you need to download Substratum and Andromeda. The app provides a tutorial for both versions.

Overall, Complete One UI - Substratum System Mods is an excellent app for users who want to fix the annoying UI bugs on their Samsung devices. The app is easy to use and provides a better user experience. For any questions or concerns, users can visit the support channel or XDA forum thread.