There's a lot of steel framed touring/gravel bikes out there at the moment. Fairlight, Bombtrack, Curve, Chumba, Mason, Brother, Norco,
Ribble, Maverick, Otso, Breadwinner, Rodeo Labs, Ritchey, Sklar, Black Mountain Cycles, and Kona. Just to name a few manufacturers.
My own bike the Kona Sutra LTD is a steel framed gravel/touring bike. It's based on the famous Kona Sutra touring bike but kitted out as a gravel bike. So you get to choose, traditional Sutra with 3x groupset, Brooks saddle, mudguards and rack. Or go for the LTD which for my bike has hydraulic discs, 1x groupset, flared handlebars and room for wide tires.
In the 5 years I've owned mine I've modified it quite extensively and covered over 15,000 Kms. A big chunk of those kilometres have also been touring mostly off road on gravel and single track.