Can’t get YouTube on iPhone because it's saying I need to update to iOS 14?

Hello~ You can’t update your device any further than iOS 12,5.7. If you need a higher version of iOS such as iOS 14 or higher you will need a newer iPhone. Click below to shop for a new device…

iPhone - Apple Official Site

If you purchase a second hand device please take a moment to read these helpful links by clicking on below to make an informed decision…

Activation Lock for iPhone, iPad, and iPod touch - Apple Support

Also:

The All Too Common SAD Reality of Buying a Used iPad/iPhone

~Katana-San~

The iPhone 6+, released by Apple over nine years ago, cannot be updated beyond iOS 12.5.X. It is considered obsolete by Apple.