According to various contemporary news reports, the Queen is upset over the use of the Cambridge family's use of helicopters to transport the entire family together. In the event that the Cambridge line of succession was to be extinguished in some way, the Duke of Sussex (the royal formerly known as Prince Harry) would be second in line to the throne, after Prince Charles. If Harry has a valid claim to the throne after all this stuff they've been going through, he would become heir to the throne, and King Harry and Queen Meghan would then take over!
This would make a great dream sequence for the next series of The Windsors, but potentially quite a nightmare for everyone else in the real world!
I'd stick to the old horse and carriage from now on.