I see, quite niche indeed.

There are still a few, though.

For Solarpunk, you have the whole slrpnk.net instances with several communities such as !solarpunk@slrpnk.net

!lego@lemmy.ml exists but is quite quiet.

The rest is indeed probably too niche. These communities won't happen here until we have a more stable platform (which Sync contributes to), with moderation tools, RES-like navigation etc.

Then, we'll probably be able to suggest to some communities to massively move here. That could work, and even if it's only a few, that would already be a victory to keep away from what Reddit has become.

In the meantime, I just think that a lot of Lemmy users keep an eye on Reddit for such communities.