If I were them I would stop reading the tabloids. Let a PR team with that and issue libel cases every time there is a lie, as Meghan claims.
Close the Instagram down, or keep it only for work. Commenting on trips, charities etc, no personal stuff at all.
Get some really good therapeutic help.
Ask other members of the RF how they coped, what worked for them etc. As someone upthread said nearly all of them have faced unpleasant media scrutiny at some point.
Work on mending bridges - turn to family members who love and support them. It seems William and Kate are not people they turn to for whatever reason.
Concentrate on what they do have , which is a lot, and stop focusing on unfairness, lack of freedom etc.
The problem is that M has spent her whole adult life courting public opinion. She is used to being lauded, people telling her how wonderful she is I suspect. Being in the RF is the reverse in all senses to what she is used to. It's a thankless job in terms of public opinion, you have to develop a lot of inner resilience and draw on reserves that you create through good friends and family. She has only one member of her family who provides this, but there are many members of the RF who can help them if they put aside their pride to ask.
I don't think they should take press intrusion lying down, but they also need to learn to keep their private thoughts and feelings to themselves and focus on their 'work'. Of course a stiff upper lip isn't particularly healthy, they need to speak to therapists friends and family, not go on TV to complain about how hard things are, and how 'unfair'. I also don't believe the media in the US are fair. They may not be as bad as they are here, but all the press are the same, they want to sell papers and enjoy digging for dirt. I think a lot of the criticism they have received has been fair.
I see Harry under huge, unbearable pressure trying to keep Meghan happy. I see it causing rifts in his own family and a lot of stress and strain. He is going to be forced to choose between his wife and his country in the end, i have no doubt. They will probably move abroad, and somehow I can't see him living in Canada very happily.
What are they going to do there? She can't go back to acting, and he will be isolated from his family and all he knows.