There are plenty of independent communities that exist. In my opinion Facebook has hurt a lot of these group, but if you look they still exist. Similarly there are plenty of independent Discord and IRC servers depending on the hobby. I have a feeling that any aggregator will just end up lowering the quality of posts in the end.

As an example, here is a unicycling discussion board that has been active for 20+ year and was a newsgroup prior: https://unicyclist.com/

There is a similar yet, different community of unicyclists on a Discord server (I won't link, but it's easy to find). And Facebook Groups has a few more communities. There is some overlap between them all.

I'm not sure what you are looking for, but if you have a specific hobby or interest, I'm almost certain a community exists and is likely a few searches away.

*Fun fact, Gilby created TinyURL in order to shorten links in the unicycling newsgroup. https://en.wikipedia.org/wiki/Kevin_Gilbertson