If you want to stick with the official experience, you must manually install a compatible APK. These versions are verified to work with the (Android 7.1) level:
Since you are bypassing the Play Store, you must enable "Unknown Sources" on your device: youtube apk android 7.1 2
: A popular open-source client that provides a smooth YouTube experience on older hardware without requiring Google Play Services. It is frequently cited as the best way to bypass the "Update your app" nag screens on Android 7.1.2. If you want to stick with the official