New Sprite Atlases and UI

Hi, currently Im trying to switch to new unity atlases system but I have problem.
All UI elements are on the scenes which are additive loaded. Each atlas I use have a variant for low memory devices (IOS/Android) and have disabled "Include in Build" options but is in Resources folder (maybe later will be in assets bundles).

Now depending on this example https://docs.unity3d.com/ScriptReference/U2D.SpriteAtlasManager-atlasRequested.html Im trying to load desired atlas but those events sometimes are not fired or when it is called and i load and pass atlas most of the ui images are white.

Any guides how to use atlas variants in UI?