Here’s my two pennies worth ...
Camilla has a cold. William has a cold but has to go out to put on a show.
Philip is very poorly and on his last legs. The family colds will not be helping.
The Queen has had a word with William and said that there will be seismic changes coming within the next 5 months to 5 years. Charles may be the monarch but William has to be seen to be The King.
I think they all know that this is the last time The Firm is in its present incarnation and they’re all tired, anxious, filled with a feeling of dread and mightily pissed off that they have to be happy clappy for the gawping crowds. I expect W and H are getting flashbacks to 1997 when they had to comfort the crowds who were wailing and gnashing their teeth and accusing the RF of not loving Diana as much as they, total strangers, did.
I think this has absolutely nothing to do with Meghan at all.