At my current job I just asked a coworker in chat if the reply was his or LLM. He quickly owned up and the incidence of brokered LLM messages in chat dropped signficantly.
Unfortunately people are being encouraged to use LLM in docs, emails, and presentations so it's probably a losing battle.
That's a better approach than what I did, and I'll use that going forwards.
We had an exec show how he was using AI to write interview feedback from his very sparse notes, in front of a few thousand people.
We have a LLM bot in chat that analyzes bugs when.you drop in a link and anything else if you ask it directly. It's actually quite effective: all the slop is now localized and can be ignored/blocked easily, and people no longer feel the need to copy and paste slop themselves.