This is the most reliable modern solution. While the original NewPipe Legacy project ended in 2021, community forks like NewPipe Legacy Revo continue to fix playback issues for Android 4.1+ devices. Lightweight, ad-free watching with background play. Where to find it: Check the latest releases on GitHub - NewPipe Legacy Revo 2. SkyTube Legacy
The original YouTube Vanced generally required for its early versions (like v13.x), and later transitioned to requiring Android 5.0+ . youtube vanced android 41 2 apk best
Team Vanced received a cease-and-desist from Google in March 2022, and the app's core playback features were officially rendered nonfunctional by April 2023. Recommended Alternatives for Android 4.1.2 This is the most reliable modern solution