An easy (but pricey) solution would be an ‘event tick’ that checks if:
-getViewportSize | BreakVector | if X>Y then: use landscape UI, else, use portrait ui.
(optional) Set (in UIWidget) LandscapeBool (true), else, set as (False)
You can either set both ui’s independantly or have it (a single UI) rearrange itself based on a condition set by the action above.
Hope this wrks 