I made Stroganoff with grain fed veal and on another day with firm tofu.
Interestingly enough, my carnivore boys prefered the tofu version.
From several old cookbooks and some trips to Russia I lean towards the belief that stroganoff is, within a large frame of “required ingredients” very much of an independent “wing it” recipe, akin to the large variations in, to name only one, crawfish etouffe. Over noodles appears to be a US invention: more “authentic” versions call for fried shoestring potatoes.
As a child outside NYC I grew up on a version similar to grillades: floured, pounded meat(sirloin was the call, chilled stiff and sliced thin) browned in butter, then the onions etc. Beef broth/wine went in but not much: the thin sliced beef did not need much…some Russian recipes merely tossed the raw, thin beef in butter scant moments before onion etc finished the base. The recipe of yore I knew then added some brewed coffee and only sour cream after simmer of, oh, ten minutes? The “elegant serving” put it over wild rice which is how I still make it. I thought the coffee touch might intrigue you.
Creme Fraiche is something I’ve used for years. I can get that closer to the real tang of Russian sour cream. The dill suggestion is sensible but might get lost. I’ve seen a judicious amount of lemon rind, as zest, tossed in. Background “sounding board” of mustard can work but I prefer not to get too complicated
And if I had excellent mushrooms, with serious flavor, I’d try not to shout those down with, say, mustard.