"friends" is not limited to people that you grew up with, or studied with, or people that your parents knew. They can also be contacts that you made by reaching out, in social circles or through shared interests or tecnhical workshops, etc.

I think the first thing to do is to recognize the need for forming connections and start working on the skills that foster those. Technical people tend to not be great at softer people skills & communication, so that's something you can start working on. I advise against just starting to reach out to people, that isn't effective usually, but to start working on the skills necessary and start looking for the situations you have access to that do foster connections.

Also, when you are on the other side, recognize that offering connections to unconnected people is a wonderful act of charity.