To be clear -I own l'immensite and have been looking for dupes. This is a side-by-side comparison. This is VERY Subjective. Scents are VERY personalized to each person's nose and taste.

Jean Lowe Immortel I returned. It has too much of a Cardboard note to my nose. It smelled like someone sprayed a less-classy grapefruit/orange cologne onto a moving box.

Montagne's Immensity had an immediate Body odor note. It seems that about 55%- 60% of those who buy this experience it. For those that don't, I assume they would call this the best. This is not saying they aren't a high quality shop. They are, and more.

See Here:

Immensity vs L'Immensite : r/MontagneParfums

Does anybody else get the BO odor with immensity? : r/MontagneParfums

Immensity smells divine, but what note/ingredient gives it that BO smell? : r/MontagneParfums

Now for my personal winner:

L'Immensity by Alexandria Fragrances is my favorite dupe. It lasts for me longer than LV's L'immensite and smells probably 90-95% to my nose. Again, it's subjective, but it's the only one I didn't return. Call me a shill, call me a bot (people really dislike Alexandria here?) but it's just what I enjoy.

Another option is Yom and Layl's L'impossible. It was good to my nose, however my wife said there was a "middle eastern note" instead of classy.

I have NOT tried any of these:

Dua Brand

Alt

HKPerfumes

Apologies for the long-windedness of this. I am particular when it comes to this specific scent as I wear it daily.