Hysperia was an inhabited planet. It had native lifeforms that resembled dragons from Earth mythology, and was thus colonized by the Hysperians: "Ren faire type" Humans who sought to follow a medieval fantasy-themed lifestyle. The Hysperians lived in castles on the planet's surface, and kept the dragons as pets. The planet was ruled by a monarch, who in 2381 was Queen Paolana. (LD: "Where Pleasant Fountains Lie")
Before committing to Starfleet, one of Commander Jett Reno's odd jobs was fixing comms relays near Hysperia. (DIS: "Labyrinths")
This planet was only mentioned in dialogue.