It looks like every comment here is suggesting that lonely people should do something to feel less lonely. But that's not how you stop an epidemic.
The epidemic is a systemic things, and you don't solve systemic things by giving advice to individuals. You solve systemic things by changing the whole culture. and you change the whole culture by large scale initiative.
That said, I have no idea about what to do!
I firmly disagree.
I do agree that the advice being given for individuals is very misguided. It's like preaching to a nearly empty church about why more people should come to church. You're only going to reach the ones who are already there.
But in this case, systemic solutions don't exist outside of (a) individuals taking action, and then (b) that action having a real impact, and then (c) the individuals, actions, and impact snowballing into a movement.
My whole question from the start was, what should those (a) individuals do, to successfully get to (b) and (c)? I did not word this clearly at all.