I knew it!
It was already pretty clear that the overworked and underappreciated knight commander was a projection of the author's own feelings of being overworked and underappreciated, but... nice that the author has made it official?
"What is manga?"
What the? But haven't they shown modern appliances in the bkg? I guess that likely implies that to them, those modern appliances are unknown relics.
This means it is very likely that this is one of those stories where they are actually in a far distant fantasy future. WHICH opens up scifi elements into the mix of explanations for the dragon's bizarre nature.
Maybe the Dragon was a product of the future but something went wrong and restarted Human progress back to middle ages by devouring modern society etc... (maybe? idk... but you got a good theory, I even re-read previous chapters just to find modern appliances that you pointed out and, you're right!)