As an active user (completely unaffiliated with Tlon), I can say that communities are truly booming on Urbit right now. Their newly released OS1 is pleasant to use and quite functional. The discourse in the many notebooks and chats I'm a part of is lively and engaging. If you're curious, boot[1] a comet[2] and message me at ~wolref-podlex—I'd be happy to set you up with a planet.

[1] https://urbit.org/using/install/

[2] https://urbit.org/using/operations/creating-a-comet/