Below is a report on the current methods to obtain and run YouTube on these devices. 1. App Store "Last Compatible Version" (No Jailbreak)
Connect your device to a PC/Mac, drag the IPA into the sideloading tool, enter your Apple ID, and install. Limitation: Youtube.ipa For Ios 9.3.5
Because these apps are modified to run on unsupported firmware, things break over time: Below is a report on the current methods