Check out networking events
If you want to learn how to make friends as an adult, think like someone looking for a new job. Job seekers often seek out networking opportunities, where they can meet, and connect with other folks looking for the same thing.
Look for places where people gather who are searching to create their next iteration, be that a new career or acquisition of a skill. Job fairs and networking events are sponsored by local government offices, libraries, and AARP, among other organizations. Get onto mailing lists and attend things that sound interesting to you. Make sure to chat with people while you’re there, and exchange business cards or personal information so you can stay connected.