Whatfly indicated the Matuka is still popular in N. California. The only places I have fished in Northern California are Hat Creek and the Upper Sacramento (Above Shasta).
While fishing the area, I went to the largest fly shop around that area....The Fly Shop in Redding. Quite a nice shop.
Just searched their site for Matuka flies and the only one that came up was that Whitlock Sculpin pattern which is not the simple straight Matuka fly pattern..............