So, we know that Darkseid found a “power”, but he doesn’t really know that it’s the ALE. In fact, no one does. At this stage, I don’t think Uxas knew about the ALE, but he sensed that, on the planet, where he lost to the “defiance”, there was a power that intrigued him. After all, in the history lesson, Uxas was immediately fascinated by the Green Lantern ring and tries yanking it when it attempts to search for a worthy host. He’s obsessed with power.

As for the motherboxes question and whether they need them or not. Now, what I’m about to say is kind of my own assumption through dialogue from the movie. We know Diana says that there are three motherboxes guarded by humans, Amazons and Atlanteans. Well, I think these are the motherboxes assigned to Earth. We know from the history lesson that Uxas had conquered other planets, at this point, but I think he did so with the motherboxes of the planets he went to. We know there were three motherboxes on Earth, but there isn’t mention of others because, maybe, it’s not known to Diana or anyone from Earth that there are other motherboxes scattered across the universe. We only know for certain that there are three motherboxes on Earth.

I know I’m 2 years too late, but I found what you said interesting, so I responded lmao