I just saw someone mention community gardening, and I'd like to expand on that.
I work in a community garden project, which coincidentally has a fair number of neuro diverse people coming along. A lot of them decided to come because they have social anxiety (very severe in some cases) but the garden gives them a place to be alongside others without necessity having to be engaging with others.
There are always plenty of things that need doing, from repetitive mindful tasks like sorting seeds from pods, to full on engineering tasks, photography, recording bugs, endless wheelbarrowing to tire you out, herb beds to get lost in.
If you're a learner gardener, you'll get a feel for what happens at what time of year and you can then replicate this in your own garden and learn from other volunteers. If you have to many seedings you can take them in, if they have to many seedings, you can take some home. We give our excess fruit/veg to our volunteers to take home, but also to our local Pantry. Our garden improves the local community, in terms of nature/biodiversity, and appearance, it makes other people smile, they like to be there, so it enhances other people's lives.
I know how hard some volunteers find it to push themselves to come, sometimes it takes a few years before they feel comfortable, but it's worth it to see friendships developing in people who thought they would never belong anywhere, and that no one cares about them.
Social Farms and Gardens is an organisation which has a directory of community gardens, might help people find their nearest community garden.
I describe myself as a community gardener, when I walk my local areas I notice what's growing, when I see a patch of verge, I'll chuck some wildflower seeds down. I've just noticed sometime else has started planting primroses in a verge I've been tending! That made me the happiest I've been all week!