For the average user, sailing the high seas for a Youtube.ipa and dealing with sideloading certificates is a nightmare. For the enthusiast, bringing an iPad 2 back to life as a YouTube viewer for the garage or kitchen is a deeply satisfying victory against planned obsolescence.
next to the app. When prompted with "Download an older version of this app?", select Limitation:
While Apple offers a feature where it lets you download "the last compatible version," this feature often fails for apps that have drastically changed their architecture (like YouTube) or if you have never downloaded the app on that Apple ID before.
If the app continues to crash, using a web browser is often more stable for older hardware.
Using third-party methods to install apps comes with risks, such as potential malware or app crashes. Use at your own discretion.