Best way to do fullscreen fade in/out for mobile?

I’m wondering how to do fullscreen fades when deving for mobile?

There’s a few options I think; A huge poly with a dynamic material, using a large fullscreen UMG image or matinee.

A poly fading in and out might double rendering time on mobile as transparent objects are a big no-no and more so if fullscreen (according to my current understanding, haven’t tried it).

I’m not sure which way is the most flexible and less problematic for mobile.