Bring a large pot of heavily salted water to a rolling boil. Add the linguine and cook according to package directions until al dente. Reserve 1 cup of the pasta cooking water before draining.

While the pasta cooks, melt the butter in a large skillet or deep pan over medium heat. Add the minced shallot and cook until softened and translucent, about 3-4 minutes. Add the minced garlic and cook for another minute until fragrant, being careful not to burn it.

Pour in the dry white wine and bring it to a simmer, scraping up any browned bits from the bottom of the pan. Let it reduce by half, about 2-3 minutes.

Reduce the heat to low. Stir in the heavy cream, Parmesan cheese, lemon juice, black pepper, and red pepper flakes (if using). Gently simmer for 3-5 minutes, stirring occasionally, until the sauce slightly thickens.

Add the drained linguine directly to the skillet with the sauce. Toss well to coat the pasta. If the sauce seems too thick, add a few tablespoons of the reserved pasta water, one at a time, until it reaches your desired consistency.

Gently fold in the flaked hot-smoked salmon and the chopped fresh dill. Toss carefully to combine, ensuring the salmon breaks into smaller pieces but doesn't completely disintegrate. Heat through for just 1-2 minutes. (If using cold-smoked salmon, add it now along with the dill and toss, only heating for about 30 seconds to warm through slightly without cooking it further).

Taste and adjust seasoning if needed. Serve immediately, garnished with extra fresh dill and a sprinkle of Parmesan cheese.