Modern coal stoves that are convenient and clean?

Well, if you can find a "coal stove" of the design common in the first 1/4 of the 20th century, I'm sure it will be as clean and convenient as anything modern. My grandmother had such a stove up until 1950 or so when it was replaced by an electric stove. I believe the main reason they were replaced was that they weren't much fun to use in the summer.

But on a cold, winter (or even summer) morning, they were GREAT.

Your biggest problem will be finding some of that scarce high quality W. Va. semi-soft coal. Anthracite and coke used to be available but were a real PITA to get going, not to mention keeping the fire up, plus there was a tendency to warp the grates because of the high fire temperatures. Back in the 1920-30's a favorite coal in the midwest was Pocahontas. In that era as well, Cannel coal from Britain was a big item on the west coast for use in fireplaces...no one then ever had a real furnace. Given a decent fuel, most of the available modern stoves ought to do pretty well, and fewer worries about chimney fires.

Joe