This game just popped up in a PCGamer article, which got re-tweeted (originally from 2021), so:
Vedelem is a real time strategy game, so not exactly what we normally look at, but this seems to include some building, and is set in a historical scenario, which makes it interesting for us. The Mongol invasion is also a not-overused scenario, so it might be worth having a look.
It seems to be a survival game though, so not fixed end goal or campaign.
It's available for free on Steam.