It looks like some American opera companies get it right:

San Diego production of Lucia, Peter Hall designs

Spot on for 17th century Scottish aristocratic dress. There are other photos of this production around the web. Looks great. And there is a dramatic point to this. Scott knew those characters well. They were fond of the same kind of ostentatious personal display that aristocrats all over Europe went in for. It's well documented in their portraits. Scott's novel is an arranged-marriage story, about a conflict between love and familial wealth and power; displaying that wealth and power in their fashion sense underlines the point. The designers of the 19th century productions got this right, and dressing the cast up in an austere nationalist uniform gets it entirely wrong.

Meanwhile I found a review page on an English National Opera production that has one of the male leads in a short kilt of the modern type that did not exist anywhere at the period when the story is set. I have yet to be impressed by anything ENO has ever done; they seem extraordinarily fond of fucking things up with gratuitous modernist anachronisms.