You do need a jailbreak. Follow this method using AltStore (works on Windows/Mac).
To install these, you will need a computer and a tool like AltStore or Sideloadly. Connect your device to your computer via USB, select the IPA file, and enter your Apple ID to sign and install the app. 3. Alternative Web-Based Solution youtube ipa for ios 12.5.6
Before installing the stock YouTube IPA, it is worth noting that on iOS 12, many users prefer modified IPAs. Apps like (which adds ad-blocking and background play) or YouTube++ were historically very popular for iOS 12. You do need a jailbreak
