Unlike many modern open-source clients, SmartTube maintains a codebase that specifically preserves backward compatibility for devices running Android 4.4 and higher.

NewPipe is a legendary open-source YouTube client. While the main version requires newer Android releases, the developers have historically maintained a "Legacy" version specifically targeting Android 4.4 through Android 5.x.

The absolute simplest way to bypass app limitations is to use a web browser instead of an application. The YouTube mobile website does not enforce API version checks on the client side.