not really a subject for the framebuilder's forum. Anyway, you possibly could find something interesting at NAHBS. Rivendell is a bike marketer, not a builder. Their bikes have been made by various companies. Waterford/Gunnar is a big name.
Re: Rivendell; fyi to the OP: Toyo, in days before Waterford/ Gunnar.
Re: Lugged steel framesets? LOTS of artisan builders. Almost every major city will have at least a few high-quality custom builders nearby (Portland is happily blessed with more than 30).
As for mass-produced lugged frames? You'd have to look at mid-sized companies, like Soma for instance, who still make one or two. Lugged frames are time-consuming to build and as a result they've become a rarity from the large companies like Trek, Giant, or Bianchi, that build in industrial volumes (mostly in China or Taiwan), which implies construction processes (like TIG welding) that are well adapted to assembly line production.
If you're interested in lugged frames, try hanging out in C & V; you'll learn a lot.
Trek 820 (650b), Univega Rover 10 (650b), Trek 930, Fuji League, Bridgestone RB-2, Bridgestone XO-3, Soma Smoothie ES, LeMond Buenos Aires, Torelli Corsa Strada