The real test of a program that replaces one portion of an image with another is an image that has more structure to the dividing line between the original and replacement.

I don't have Luminar but have done a few sky replacements and other replacements. In the examples, the mountains present a pretty clean edge between the earth and the sky, so it's not a big problem to replace the uninteresting blue sky with something else. How about some examples with some trees with leaves on them? With sky showing between the branches and leaves? There's a lot more structure in that sort of division. An extreme example is hair. And an even larger problem occurs when the background being replaced is not uniform, and even worse, when it contains colors similar to the foreground.

I believe that sky replacement occupies a relatively minor place in the universe of replacement of elements in images.

What was the intended main subject of this image, the tree or the sky. In the first photo it's very clear that the tree is the main subject. In the second image, the replacement sky seems to be fighting the tree for dominance as the main element and even partially obscures it. The replacement sky is very interesting, but I don't think it's appropriate for this particular image.

if this was just an experiment, that's fine, but I think the original sky serves this image better. I suspect that many people may overuse very dramatic replacement skies to the detriment of the overall composition.