Clubs don’t end after high school and/or college. Join local clubs that match your interests. I joined a local rec center tennis team, snowboarding in the winter, go ride biking trails. A lot of my activities I go to solo but so do so many other people. I’ve met so many wonderful people this way. Just be open to meeting and talking to new people!
Also, volunteering! I know two friends personally who are in long-term relationships with people they met this way.
I haven’t been looking to date but you easily could meet your other half by being more involved in your community.