However they did it, it’s beyond the limit of my immediate knowledge. 
An observation: There are “WPO” scalars inside of that material. It looks like they animated the ships using “World Position Offsets” (Basically changing vertices location inside of material without any external animation/keyframes)
As a path forward, I would watch many different “How to make a portal” videos for UE4/5, and then try to migrate those methods into UEFN. Also, there are several portal examples on Fab that could be dissected.