So I've found the Duraludon just vibing out in my Shield boxes, alongside a couple other extra shinies.
None of them are Dragon type unfortunately, but there is a Gyarados amongst them and although not actually a Dragon type, to me it's always looked like one. It's not a bred shiny or anything. I have both HG and SS and transferred both the fixed shiny Gyardos' over to Shield, so one of them is spare =P Should that be of interest.
Anyway the shiny Duraludon:
-It's in a Level Ball, and is a male.
-It's still level 1 as I didn't touch it after hatching.
-It has it's HA: Stalwart.
-Rash Nature, probably not the best nature for it, but Sp Attack is it's better attacking stat and it does boost it. Lowering it's already low Sp. Def is probably not the best option though =P People could always use a Nature mint on it though.
-It has all 3 egg moves Duraludon can have: Slash, Night Slash, Mirrror Coat.
-It currently can't Gigantamax, but I can easily feed it some Max Soup so that it can; if the recipient wants it to be able to Gigantamax into a skyscraper.
-Shield is the game I bred it in, though I do remember putting it in Sword at some point. I might still be able to nickname it since it's back in the game where it's egg was hatched.