First, what mechanisms exist (if any) that make known the availability of an alternative venue? Right now, the only thing I can see is the occasional "I'm leaving, and here is how to find out where I'm going" Meta post.
Some might be thinking, We can't expect management to permit this to be done explicitly.
The response to that might be, We won't know until we try; and management has made clear that they their focus is the big technical sites, where they are hoping to .
Second, what other mechanisms, if any, could be added?
What is the apparent boundary between what is permitted and what is not permitted?