negi

Mario Art - it’s just Mario Paint.
Hearts of Ion - very complicated particle physics simulator.
Imworld - you can trigger challenges at your will.

Lemmy Explorer is very useful for seraching Lemmy communities.
https://lemmyverse.net/communities

It looks like there are some guitar communities already.

kbin.social has 29.8k local users.
157k is local + all federated servers.

kbin.social will also be defederated from beehaw.org, sooner or later.
After all, it has open registration policy and many users too.