A portrait recorded video cannot be uploaded to You Tube

Hi,

I have recorded a video with my new iPad Pro 12,9.

Now I would like to export it to You Tube. What I do is I go to Share, I rennder ut which takes quite a lot of time and than a I get to choose which social media I would like to export it to. You tube is not among them.

Why? Could the reason be beeing recorded in portrait mode? The smallest size I can export it to is 720x1280.

Is there a way to put it into You Tube obligatory landscape mode and have black margins on left and right?

Please not that cropping is not an option as everything what was recorded on the screen should be seen.

Last but not least, I do not even know where in Rush to do that - increase mz portrat view to landscape bz adding black marings to left and right.