It’s dumb and doesn’t tackle the root of loneliness. If they’re lonely, they need support to find new friends.

If they have trouble making friends, and it’s not due to their own personality being toxic (like being an incel, creep, borderline, or generally an asshole), then they also need support in learning how to socialise. And even if they had those toxic behaviour issues, having help to overcome those would still be useful for everyone in the long end.

But that said. It doesn’t mean they’d have to socialise, just that they learn how to do so, and so have a way out of their vicious circle. Best way to make friends as an adult (so, no school/college/uni), is to go to the circles where you have mutual interests.

So, to such people I say: go take up a calming team sport. Take up an hobby that’s relaxing and doesn’t make conflicts. Schedule IRL meetups with the people you like and know online. Go to a concert, or a bar. Or go to a lecture, you can then discuss with people afterward.

Or, a “search friends” app (like for dating?, but I don’t recommend those because they work on profit, so they often recommend the ones that barely just don’t work out, to keep you hooked.

Talking to people is scary, but try and experiment using normal, calm lines. Weather is a great topic, the relevant event to discuss about also is, to start discussions. Even if you “fail” one of thos social interactions, so what? You can apologise, explain that you find it difficult socialising, or you wouldn’t see them again. So you can just start afresh with other people and learn.