Enable Unknown Sources: Go to Settings > Security and toggle on the switch for Unknown Sources. This allows you to install APK files downloaded from your browser.
NewPipe Legacy: NewPipe is a popular open-source YouTube client. They maintain a "Legacy" version specifically for older Android versions like 4.1 through 4.4. It is ad-free and very fast. Is it Safe to Use Old Versions? Youtube Apk Download Android 4.4 2
Find a Trusted Source: Since you cannot use the official store, use reputable APK mirrors like APKMirror or APKPure. Search specifically for YouTube version 14.43.55. Enable Unknown Sources: Go to Settings > Security
Before you begin, you must prepare your device to accept files from outside the Play Store. Youtube Apk Download Android 4.4 2