Flew just fine today. Not sure these warnings mean much, unless it's a G4. If the solar storm was going to be big enough I'd think we'd see it on national news.
The Mavic and other DJI drones don't seem to be affected by solar storms.
FWIW, lots of hits turn up in the search results here when searching for things like "kp index". Those threads just contain a bunch of warnings (like this one) about being mindful of solar activity. I've never seen anyone confirm solar activity was the cause of a problem/crash.