The imgur instance, at community.imgur.com is largely non-techy, but they tend to be younger crowd who have grown up with the Internet.
There’s also the Car Talk one, which frequently gets pointed out for how to use tags instead of many categories. That’s a good example of feature I consider difficult to explain to non-techies getting a lot of use. https://community.cartalk.com/
And I’ve never even looked at it, but I know there is a huge forum for Jaguar (car) lovers. That started out as a mailing list and migrated, so the community existed prior to being a Discourse instance, but has survived the transition. https://forums.jag-lovers.com/
There’s also a list of sites here to consider: