No risk of bricking your device or compromising security. It works immediately without downloads.
If you have downloaded YouTube in the past using your Apple ID, you can still grab a compatible version. Open the App Store on your iOS 12 device. Tap on your Profile icon (top right) and select Search for "YouTube" in the list of apps you own. Cloud icon to download it. A pop-up will appear saying: Install Youtube Ios 12.5.7
YouTube will now appear there. Tap the cloud icon to install the older, compatible version. The Safari Web App Workaround No risk of bricking your device or compromising security
While this installs the app, many users find it immediately displays an "Update Required" pop-up that blocks all usage. Method 3: Jailbreak Fixes (Advanced) Install Youtube Ios 12.5.7