Forums are dead so for modern hobbies like simracing I haven't found anything. I work on old cars so there are still great forums for that stuff, and gardening I have given up on online discussion content - it's mostly crappy sponsored content trying to sell you bullshit. Gardening content is best consumed in books and YouTube and ignore online discussion.

I just mentioned it in another comment but Discord servers are one of the newest types of communities popping up (especially for younger folks, but they can be for people of any age). For example, here’s one about gardening: https://discord.gg/D2kCbGY

This is the worst possible outcome for hobby content. At least forum/reddit threads are searchable on the open web and likely to remain available at least for a while.

There are definitely pros and cons. In many ways it’s like a modern equivalent to IRC rather than Reddit/Forums.

Discord is searchable enough. Not being on the open web forever is a feature.

Not OP, but one modern option is Discord servers. There are lots of them these days on all kinds of topics.

IMO live chat is awful for community building, especially one with deep knowledge bases such as gardening. It's great for troubleshooting problems and asking questions, but it does not do a good job of retaining information, and it excludes people from obtaining information who are not there right now when the conversation is happening