Upon unboxing of my newly purchased grill, I discovered a crack in my KJ dome in a similar location as the original poster. My crack was not as severe and not as long in length, but near the hinge area and horizontal. I was able to get it resolved using the formal process, though it took some time. I am providing my timeline in case it helps you weather the wait.
April 24, 2020 - Submitted Warranty Claim
April 24 - Received response via email (same day asking for additional picture) to validate diameter. I responded the same day.
May 7 - Received email that replacement order for dome was placed, but it was on backorder until July, 2020
June 2 - Received call from shipping company to schedule deliver
June 3 - Received new dome.
I know there has been discussion on responsiveness to warranty claims and I too was worried while waiting for updates. I imagine that timelines for you may be extended due to the popularity of the grills and the pandemic. I hope that this helps in managing expectations. I was fortunate that I could use my grill in the meantime and was very excited to receive the replacement part much earlier than forecasted.