Edit: Looked it up, the French word is actually "saumon". The L in the English word probably isn't from French.
The word comes ultimately from the Latin salmon, but we got it by way of French, as we did with so many other food words. The French, as was their wont, had swallowed up the Latin L in their pronunciation, so by the time we English borrowed the word, it was saumon, no L in the spelling and so no L in the pronunciation.
Sallemonne /s
Edit: Looked it up, the French word is actually "saumon". The L in the English word probably isn't from French.
https://katherinebarber.blogspot.com/2020/03/the-l-in-salmon.html
So no, the L isn’t, but the pronunciation is.