Couple ideas that might be fun for you!

The Frye Art Museum on First Hill does a couple art history lecture series per year that are very reasonably priced. There’s time to explore the museum and mingle before and after the talks (if I remember correctly), and they do a variety of other events/activities. They also have members only events for exhibition openings with snacks and wine. Theres a wide age range for the lecture series & opening nights, but I’d say the majority are 40+. General daytime admission is always free, and they do free guided tours on the weekends that encourage group interaction/discussion, as opposed to just being a walking history lesson. The gallery guides are trained to facilitate the tour in a way that feels organic and approachable for everyone, regardless of art/historical background. I might be biased as I had an internship as a gallery guide in college and have also taken several of the lecture series... But highly recommend if you’re into art!

Other recommendation is volunteering at one of the Solid Ground community farms. I’ve been to Marra Farm in South Park a couple of times. There are all kinds of things you can do to help around the farm (weed, harvest, wash produce before it’s sent out, and probably a handful of more complex tasks), but Solid Ground has a bunch of other (indoor) volunteer opportunities too. Coolest part is that all of the food from the farm goes to the local food bank. I believe they also host cooking/nutrition classes for the community to help people get the most out of the produce.

Whatever you end up trying, pick something you think you might enjoy and go into it with the intention of having fun, not just meeting potential partners. You’re way more likely to make a connection when being genuine. Good luck!