Because Android 5.1.1 is no longer secure, using it for apps that require a Google login (like YouTube) carries risks. If you use your device frequently for media, it is highly recommended to upgrade to a device running at least Android 10 or newer to ensure continued app support and security.
While you can download legacy APKs, they rarely function without the "spoofing" mentioned above. app youtube android 5.1.1
Alternatives
Before you start downloading files from random websites, check the most common fix. Because Android 5