You cannot install these from the App Store. You must use tools like Sideloadly or AltStore (if compatible) to sign and install the IPA file from a computer.
If you find a reliable IPA for iOS 10.3.4, you can install it using tools like or AltStore (if compatible with your version). Reviewers on YouTube suggest ensuring that "Installing Apps" is allowed in your device's Content & Privacy Restrictions before attempting to sideload. How To Install IPA File On iPhone & iPad youtube+ipa+for+ios+1034+extra+quality
You cannot install a without acknowledging the risks. You cannot install these from the App Store
For users on iOS 10.3.x seeking a high-quality YouTube experience, the standard App Store version is no longer supported, as current requirements have moved to . To get YouTube running on older firmware like iOS 10.3.4, you must rely on sideloaded IPA files or legacy community tweaks. Best Legacy YouTube Options for iOS 10 Reviewers on YouTube suggest ensuring that "Installing Apps"