Anarchism@lemmy.dbzer0 is pretty active last I saw.

We’re spread pretty uniformly throughout the Lemmyverse. There are active anarchist communities (all /c/anarchism on their respective instances) on lemmy.dbzer0.com, slrpnk.net, lemmy.ml, and hexbear.net.

In their parents’ basements?

No, theyre in the woods with no technology made by a group