If you are looking for the full version of YouTube for Android 5.0 (Lollipop), it is important to note that Google officially ended support for this version years ago. The standard YouTube app from the Play Store likely won't work or update on such an old device.
The most reliable method is using a lightweight browser to visit m.youtube.com Third-Party Clients: youtube android 5 version full
Google Play Protect may flag the sideloaded app. This is a false positive. Tap “Install anyway” or ignore the warning. If you are looking for the full version
extension to block ads, which can be heavy on older processors. Option 3: Advanced App Patching Release Date: August 2022 Last Update: September 2022
to see if you can install a custom ROM to upgrade your device to Android 8.0 or newer. Google Help Why the App Stopped Working : Google ended security updates for Android 5.1 in 2018. API Changes
Keep in mind that YouTube has evolved significantly since version 5, and newer versions offer a more comprehensive and secure experience. If possible, consider updating to a newer version of YouTube or using the latest YouTube app available for your device.
How to use the YouTube app on android 5 - 7 : r/androidafterlife