If you do not have a computer, you can attempt to use third-party web signers.
To use YouTube on a device running iOS 12.5.6 (such as an iPhone 5s, 6, or 6 Plus), you must use specific workarounds because the current YouTube app requires iOS 16.0 or later Installation Methods Official App Store (Recommended)
Select .This provides a nearly app-like experience without the version errors associated with IPAs.
If you have previously "purchased" (downloaded) YouTube on your Apple ID, you can still get a compatible version directly from Apple. and tap your profile icon. Go to Purchased > My Purchases . Search for YouTube in the list.
Apple released iOS 12.5.6 in September 2022 specifically for devices incapable of upgrading beyond iOS 12. This important security update patched a critical WebKit vulnerability. The compatible devices include: