Remember when MTV was the place to go for music discovery? For Millennials (and of course Xers—don’t hurt us Gen X, we know MTV was yours first!),MTV was the place to watch the hottest videos, catch countdown shows like Total Request Live, and see what everyone was listening to that week. It was appointment viewing: music, culture, and trends rolled into one channel, all delivered through cable TV.   But those days of cable dominance are long gone. Late last year, MTV shut down its remaining 24-hour music channels as audiences continue to shift toward streaming. Across the U.K. and...