This is how difference between Lumen and Path Tracer should look like for the skylight:
Lumen (at the moment) doesn’t have a good sampling strategy for skylight and traces a small number of rays per pixel, so it will miss bright spots representing sun causing overall loss of energy. It has also relatively low spatial resolution, so it can’t achieve sharp shadows like UE path tracer.
Your images have larger differences. It may be because of the HDRI backdrop which isn’t supported by Lumen. You can check in Lumen Overview visualization what Lumen sees and if it sees proper skylight or something broken. Best would be to place that cubemap directly into skylight instead of using HDRI backdrop. Then for even better results you could extract bright light sources like sun from the cubemap and replace them with analytical lights.