My eberron game handles fly by having military fortress type places with either a good stone roof or largely underground (if not both) with a simple divination to show the sky above while inside The players get really excited by finding the whizbangWOW enchantment that literally just shows the sky & you might have a good excuse for a rooftop battleIt's probably best not to think too hard about how Invisibility, Fly, Fireball, Teleport, etc affect technological development, or the wheels will fly off your swords & sorcery game.
Someone complained that EE isn't technically "official", but siege staffs have been mentioned as part of eberron since the 3.5 days & finally have a statblock to provide no more excuse for leaving them out of 5.5/6e phb/dmg again. That it's not official comment rings hollow & shows why the omission is such a flaring problem when they did manage to include this