PICKLEBALL! I just got into it a few months ago. There are 2 hour drop-in sessions at a nearby community center three times a week, and I frequently manage to make all three of them.
Pickleball is combination of badminton, tennis, and ping pong. You can visualize it by thinking of playing tennis, but standing on the ping-pong table.
There's a huge, very friendly sub-culture of pickleball players. Many of them are standard retirement age, and many of the drop-in sessions are during work hours, but it's starting to become more popular with the younger crowd too. It's something you can learn in about 30 minutes, and start having real fun in about an hour, though mastering it is an ongoing process and can take months and years.
Also, when you travel around in the US (and increasingly other countries as well), just bring your paddle with, and you'll probably be able to find a friendly pick-up game that you can join. At the community center I go to, there's the regulars, and and frequently also people who are just visiting the area and want to get some play in.
Here's a video you can watch for a little intro: https://www.youtube.com/watch?v=qmYF67dqNaQ&t=5s
Many people, once the organized sports leagues of childhood are over, don't have any sports in their lives. I never played any organized sports, but now that I'm playing pickleball, I'm realizing how much I've been missing. Competitive play can be such pure, unadulterated fun!
And oh yeah - it's cheap. Buy a paddle ($15 - $80) and a few balls, and show up (my community center charges $2 a session, if you find outdoor courts it'll be free).
One more thing - I had heard of pickleball many years ago, and went to a drop-in session at a community center. Nobody was unfriendly, but there was also nobody who made an effort to welcome new players and show them the ropes. I didn't try again for a long time, and thus missed year of fun! I later learned that that particular location was known for having quite advanced players. Don't make my mistake. If you find that a certain drop-in pickleball session is not the right place or is too advanced, don't give up, try another place, or take a class. Pickleball options around the country are exploding.
Let me know if you have any questions! I'm trying to spread the awareness of pickleball. Also, PM me if you're in the Seattle area and want to try it out, I have spare paddles.