I'm looking to buy the english version of 'I Became the Demon Lord so I Created a Dungeon and Spend Heartwarming Time There with Non-Human Girls'. has it got an english publisher yet?
Check the information sheet of the novel. There's the Original Publisher and the English Publisher section below the tag list. If there's no english publisher yet, there'll be a N/A written. That's the case for your novel. Be aware of the fact that having a publisher doesn't always mean having a physical version coming out (if that's what you were looking for). Most of the time, it only means they handle the english digital translation.