there are and have been conversations around the fediverse about this very same concept or need. See, eg, a cousin comment in this thread on the same idea: lemmy.ml/comment/7026804
And the short answer is no … the fediverse basically sucks at providing such a thing … so enamoured is it with federation that localised communities are obviously a bit of an afterthought. Thing is people actually want and need more private or local spaces as well as the big public spaces. Its why all the old school forums are still kicking.
And the worst part is that federation offers a great opportunity to provide both in a really useful and seamless manner on a single platform. But neither lemmy nor mastodon have a feature for it (with mastodon lead dev actively opposing the idea it seems).
I have to believe it would be easy for lemmy to implement.
As a contrast, misskey and its forks such as firefish, catodon, iceshrimp etc (and yea, these names are a choice, in a good way I think), actually provide local only groups and people like them.