No, but there is on PieFed.social. Mods and admins have functionality to check any post or comment for LLM-generated text. There's more stuff too.

Generally I share my findings with Lemmy admins so they can ban the account.

I think this is a pretty big threat to the fediverse and social media in general and am taking it very seriously. At the moment the amount of slop is pretty low but we need to be ready for the deluge when it comes.

My instance bans non-consensual AI content and users. Rimu's tools have made that a lot easier to do, I get an alert when the system detects a possible AI user.