Hey all! I've created a MSFS thread on this about a year ago... of course, zero response from the devs.
However, today -- low and behold - LIGHTNING and thunder are back in live weather. Was just at Atlanta and was able to record it (apologies, you also will hear me scream at my puppy for peeing on the carpet while this was happening! oops!)
Latest thoughts (June 2023) - I recall Seb or Jorg mentioning that lightning and thunder never went away from the sim, it's just that we weren't in summer months... yet, I don't guess they realize that at least in the south US/southeast US, we get lightning in real life ALL YEAR round.
Check it out!