Wow.
IF THIS IS TRUE it's rather terrifying.
I'd not heard of "dark lightning" (so I will do some digging
Not a threat to people on ground but possibly to planes that get close to thunderstorms.
Little gamma ray bursts. Any exposure to gamma radiation is very bad.
ExtremeTech: Scientists Calculate How Often 'Dark Lightning' Could Strike Passenger Planes.
https://www.extremetech.com/extreme/342627-scientists-calculate-how-often-dark-lightning-could-strike-passenger-planes