Oh cool, I didn't know that! All the time I've been around Muscovies, they were in with a bunch of other ducks and chickens and things.. I did know they hiss though.
My great grandma used to water candle close to hatch eggs (chickens), but she'd place them in a thin baggie or stretch saran wrap across the top like a little egg waterbed, then water candle.
I couldn't say if this ever harmed any chicks, she always had great hatch rates. I think it was a last...
Maybe you can try water candling, but I'm not sure if it's safe to do in lockdown... maybe if you use very warm water?
The best bet is to probably sit and wait.:fl