https://avherald.com/h?article=51c0816b&opt=0(couldn't hear the original emergency declaration on JAX or MIA, and we also had a little bit of weather the Centers were dealing with,
so from the hand off to landing at KPBI attached)
A Southwest Airlines Boeing 737-8 MAX, registration N8889Q performing flight WN-3204 from Chicago Midway,IL to Miami,FL (USA), was in the initial descent towards Miami when the crew observed smoke from a cell phone on the flight deck and decided to divert to West Palm Beach, where the aircraft landed without further incident.
The FAA reported: "Southwest Airlines Flight 3204 landed safely at Palm Beach International Airport around 6 p.m. local time on Sunday, August 4, after the crew reported smoke on the flight deck from a cell phone battery. The Boeing 737 MAX departed from Chicago Midway International Airport and was headed to Miami International Airport. The FAA will investigate."
The aircraft is still on the ground in West Palm Beach about 21 hours after landing.
https://flightaware.com/live/flight/SWA3204/history/20240804/1920Z/KMDW/KMIA