Sukhoi's Jumbo Jet (KR-860 which never happened)

Closer to a 380 than a jumbo in having full length double deck. Take out the ludicrous bits (ventral escalators) and it's a rational design. I guess folding wings was for the same reasons people do it now: airport technology/wing-length assumptions.

The elevators are entirely rational for use in less developed airstrips, but not for volume passenger use.

I wonder if LNG engines would have had as much thrust? It's lower energy fuel but I have no idea if it's lower ISP if that is part of the turbine equation: GE and RR engines are used for gas electric generation so it obviously works.