Well,that cleaned up nicely.
I pulled a 27" wheel out of the free pile at WTF Bikes and disassembled it into (Weinmann Concave) rim, 36 grubby spokes, and one absolutely filthy Sovos hub. The spokes are in two heaps waiting to have a degreaser bath, the rim is lying around while I decide whether to cut it down to 650b (which would make it a 34 hole hub, which would be, um, kind of unique), and I pulled the hub apart and completely rebuilt it. It was amazingly gross; it was caked in stick black grease (I suspect a combination of enthusiastic chain re-oiling and the grease from the inside that got washed out) and there had been enough water intrusion on the nds side so that the grease there had turned into some kind of toxic taffy.
But that wasn’t a worry, because I zapped it with wd40 until the goo came off the outside, then disassembled it and cleaned the disgusting horrible taffy out of the bearings, cleaned the inside with wd40, then dried it, repacked it, and readjusted it. And the freewheel? An old 14-21 5-speed freewheel (“Atom” brand, from France, and possibly British threaded but probably not – I need to clean the threads, grease the devil out of them, then attempt to thread it all the way. And if it doesn’t fit, why, I could just take spacers off the ds axle and make it into a very narrow single-sided suicide fixed hub.