The Tech Guy's Transmigration

Rodney, an engineering geek, transmigrates into a minor royal—instantly lumbered with a wife, a wasteland fief, and debts from three exiled ex-wives. Bankrupt and bandit-plagued, he rebuilds civilization with modern know-how: gunpowder, smelting, firearms, perfumes, rainmaking—you name it. One man, one mission: reboot a dead land.