LONDON—Jamal Edwards, a British music entrepreneur who championed U.K. rap and grime and helped launch the careers of artists including Ed Sheeran, Jessie J, and Stormzy, has died. He was 31. His mother, broadcaster Brenda Edwards, said Monday that her son died the day before after a sudden illness. She said the family was “completely devastated. He was the center of our world.” Edwards founded the online music channel SBTV as a teenager in 2006. Frustrated that he could not find the music he loved online, he began filming performances by friends in his west London neighborhood. SBTV now has more than 1.2 million subscribers on YouTube and has helped a generation of performers, including rappers like Stormzy, Skepta, and Dave, gain national and international attention. “It was a frustration of going to school and everyone talking about ‘How do we get our videos on MTV,’” Edwards later recalled. “YouTube …