You must install an older version of YouTube that was the last to support Marshmallow.
The official YouTube app from the Google Play Store no longer supports Android 6.0.1. If you have an old phone or tablet running Marshmallow, you cannot install the latest version of YouTube. However, you can still watch YouTube using an older compatible APK or a web browser. youtube apk android 6.0.1
sometimes maintains compatibility for slightly longer on older firmware. 4. Security Considerations End of Life : Android 6.0.1 stopped receiving security updates in August 2018 You must install an older version of YouTube
This is not just a technical specification. It is a story about digital archaeology, the battle against planned obsolescence, and the quiet resilience of older hardware. the battle against planned obsolescence