I've spent some time thinking about this today. Like others on here, we've moved about quite a lot and lost contact with people. I have one friend of over 40 years standing who lives about 100 miles away and the two couples get together for a few days every year - otherwise we keep in contact by email and text. A couple of others are now email frinds only.
We moved to small market town about 10 years ago, and although I know a lot of people to stop and chat to in the street I wouldn't really describe any of them as real friends. I did all the things suggested here - joined local groups, volunteered etc. I found the best groups were those with people who came from outside the town, because people round here seem to stay in the same area all their lives and have so much interconnected history that they feel no need to let others into their circle.
However, we are lucky. DH and I have been married for over 40 years, and we'd describe each other as our best friends. We have the same sense of humour, can talk to each other for hours about any topic, both love to learn about new things. So for now, I'm happy. I do, of course, recognise that life circumstances can change, but I think that I am one of those people happy in my own company and so I'll continue to have acquaintances and cheery street conversations.
I’m finished my festival poncho