Here is a page listing block lists, where you can find plenty of "fun" servers: https://github.com/mastodon/mastodon/discussions/18143

They'll include reasons for the block, which you should pay attention to.

https://fedilist.com/ is a good instance browsing/monitoring tool maintained by the guy who runs fsebugoutzone.org, one of the more prominent and "fun" servers. He's a good dude.

You can browse by software, whether its open registration or not, allows tor, etc. You can glean statistics off of certain instances, which is really useful if you run one yourself. Most of the instances on the other side of fedi run the Pleroma software.

Have fun!