Fed Up with Being the Spoiled Queen’s Genius Butler, I Ran Away and Built the World’s Strongest Army (2021)

Blurb:
Leet isn’t just any butler. His mistress, Princess Kilik, demands the impossible—and he delivers it, seven times before breakfast. But one day, Leet decides enough is enough, and he flees for a neighboring land where the talented rise up through the ranks instead of languishing in thankless, dead-end jobs. Under a new name, Lilt, he enrols in a training and job placement program, and rapidly discovers that, easy as “wax on, wax off”, his butlering skills make him a valuable asset!

Source: www.anisearch.com/manga/59701