I have ducks myself (5 pekins) . None broody. My first (and only) attempt at incubating was a 100% failure. Its more difficult than I first assumed. May your results, when you finally have that opportunity, greatly exceed the success of my own.
I... would make a duck egg for breakfast.
Assume you have neither a broody hen, nor an incubator, the chances of putting that egg under a bird and having it hatch in four weeks seems extremely slim. So I'd put it to a known good use.
Sorry.