Community Colleges sometimes allow people to audit a class for free.
But you can also do something as simple as joining a book club. Checkout the offerings in your area at meetup.com, or check your local paper for a list of activities. Go and volunteer at an animal shelter a few days a week. Libraries often offer free programs. Colleges often offer free concerts and lectures.
You could volunteer to read to children or seniors in a nursing home. (Maybe you could find someone that speaks German in a nursing home that would be happy with a bit of company?).
There are inexpensive and free clubs for all types of hobbies including photography, chess, hiking, etc.
Some animal rescues cover food and vet bills, and your therapist would likely right a letter for you that a Emotional Support Animal would be of benefit to you (in case you live in housing that forbids pets).
I tend to be a hermit because it causes me severe pain to be in a vehicle, but walking doesn't. Since I adopted a dog a few months ago, I am forced to go outside to walk her 4-5 times a day. I've met people in my neighborhood, and getting a bit of exercise is great for brain chemistry of course. Having a dog that provides unconditional love, and that is a goofball, brightens my days! I can go from crying because my pain is so out of control, and the next thing I know I'm cracking up because she amuses me so much.
You could also join a support group...
You could get a free plot of land through a community garden and grow some of your own fruit and veggies. If you participate in activities that attract mellow, down to earth people, it'll be easy.
Even if all you can manage is walking a block a day at first, just look people in the eye and say Good Morning! Smile if it feels comfortable.
This is a bit of a jumble of quick brainstorming. Hope something in here has some appeal.
P.S. Just noticed you did mention meetup. Go out to a movie meetup as a first outing to try! And Tell your therapist about the German group and discuss the anxiety the thought of it brings up for you!