These are popular choices in the jailbreak community for older devices, often featuring built-in fixes for the "Update Required" nag screen.
Free Apple Developer accounts sign sideloaded apps for 7 days only . After that, YouTube stops opening. Her workaround: On day 6, she re-sideloaded the same IPA. Yes, it was annoying, but it kept YouTube working. youtube ipa for ios 12
Check out this guide on how to force the official App Store to give you a compatible YouTube version for iOS 12: These are popular choices in the jailbreak community