As others have said, it’s called a “ghost kitchen”. My partner worked at TGIFs at one point and they had a sushi ghost kitchen inside of it with a completely different name and graphic design

You could also say that Longoven now has a ghost kitchen because they opened Lost Letter within it but I also don’t quite consider that a ghost kitchen because they’re super up front about it and not trying to dupe anyone. Genuinely seems like two restaurants in one now.